Medical Genetics

The field of medical genetics focuses on how genes and heredity affect our health. This area encompasses birth defects, prenatal diagnoses, and a host of genetic diseases such as certain types of cancer, dermatologic conditions, and autism. Medical geneticists work with people of all ages.

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Diseases & Conditions
Aarskog syndrome
Aarskog syndrome is a very rare disease that affects a person's height, muscles, skeleton, genitals, and appearance. It can be passed down through families (inherited).

Diseases & Conditions
Aase syndrome
Aase syndrome is a rare disorder that involves anemia and certain joint and skeletal deformities. anemia

Diseases & Conditions
Achondrogenesis
Achondrogenesis is a rare type of growth hormone deficiency in which there is a defect in the development of bone and cartilage. growth hormone deficiency

Diseases & Conditions
Achondroplasia
Achondroplasia is a disorder of bone growth that causes the most common type of dwarfism.

Diseases & Conditions
Acrodysostosis
Acrodysostosis is an extremely rare disorder that is present at birth (congenital). It leads to problems with the bones of the hands, feet, and nose, and intellectual disability.

Diseases & Conditions
Adrenoleukodystrophy
Adrenoleukodystrophy describes several closely related disorders that disrupt the breakdown of certain fats. These disorders are often passed down (inherited) in families.

Diseases & Conditions
Aicardi syndrome
Aicardi syndrome is a rare disorder. In this condition, the structure that connects the two sides of the brain (called the corpus callosum) is partly or completely missing. Nearly all known cases occur...

Diseases & Conditions
Albinism
Albinism is a defect of melanin production. Melanin is a natural substance in the body that gives color to your hair, skin, and iris of the eye.

Diseases & Conditions
Alkaptonuria
Alkaptonuria is a rare condition in which a person's urine turns a dark brownish-black color when exposed to air. Alkaptonuria is part of a group of conditions known as an inborn error of metabolism. inborn...

Diseases & Conditions
Alström syndrome
Alström syndrome is a very rare disease. It is passed down through families (inherited). This disease can lead to blindness, deafness, diabetes, and obesity. blindness deafness diabetes obesity

Symptoms
Ambiguous genitalia
Ambiguous genitalia is a birth defect where the outer genitals do not have the typical appearance of either a boy or a girl.

Diseases & Conditions
Angelman syndrome
Angelman syndrome (AS) is a genetic condition that causes problems with the way a child's body and brain develop. The syndrome is present from birth (congenital). However, it often isn't diagnosed until...

Diseases & Conditions
Apert syndrome
Apert syndrome is a genetic disease in which the seams between the skull bones close earlier than normal. This affects the shape of the head and face. Children with Apert syndrome often have deformities...

Symptoms
Arachnodactyly
Arachnodactyly is a condition in which the fingers are long, slender, and curved. They look like the legs of a spider (arachnid).

Diseases & Conditions
Ataxia - telangiectasia
Ataxia-telangiectasia is a rare childhood disease. It affects the brain and other parts of the body. Ataxia refers to uncoordinated movements, such as walking. Telangiectasias are enlarged blood vessels...

Diseases & Conditions
Autism spectrum disorder - Asperger syndrome
Asperger syndrome is often considered a high functioning form of autism. It can lead to difficulty interacting socially, repeat behaviors, and clumsiness. Asperger syndrome is a part of the larger developmental...

Special Topics
Autosomal dominant
Autosomal dominant is one of many ways that a trait or disorder can be passed down through families. In an autosomal dominant disease, if you get the abnormal gene from only one parent, you can get the...

Special Topics
Autosomal recessive
Autosomal recessive is one of several ways that a trait, disorder, or disease can be passed down through families. An autosomal recessive disorder means two copies of an abnormal gene must be present in...

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Diseases & Conditions
Bassen-Kornzweig syndrome
Bassen-Kornzweig syndrome is a rare disease passed down through families. The person is unable to fully absorb dietary fats through the intestines.

Diseases & Conditions
Beckwith-Wiedemann syndrome
Beckwith-Wiedemann syndrome is a growth disorder that causes large body size, large organs, and other symptoms. It is a congenital condition, which means it is present at birth. The signs and symptoms of...

Symptoms
Broad nasal bridge
Broad nasal bridge is a widening of the top part of the nose.

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Diseases & Conditions
Canavan disease
Canavan disease is a condition that affects how the body breaks down and uses aspartic acid. aspartic acid

Diseases & Conditions
Charcot-Marie-Tooth disease
Charcot-Marie-Tooth disease is a group of disorders passed down through families that affect the nerves outside the brain and spine. These are called the peripheral nerves.

Diseases & Conditions
Chediak-Higashi syndrome
Chediak-Higashi syndrome is a rare disease of the immune and nervous systems. It involves pale-colored hair, eyes, and skin.

Special Topics
Chromosome
Chromosomes are structures found in the center (nucleus) of cells that carry long pieces of DNA. DNA is the material that holds genes. It is the building block of the human body. genes Chromosomes also...

Diseases & Conditions
Chronic granulomatous disease
Chronic granulomatous disease (CGD) is an inherited disorder in which certain immune system cells do not function properly. This leads to repeated and severe infections.

Diseases & Conditions
Cleidocranial dysostosis
Cleidocranial dysostosis is a disorder involving the abnormal development of bones in the skull and collar (clavicle) area.

Diseases & Conditions
Coarctation of the aorta
The aorta carries blood from the heart to the vessels that supply the body with blood. If part of the aorta is narrowed, it is hard for blood to pass through the artery. This is called coarctation of the...

Diseases & Conditions
Congenital adrenal hyperplasia
Congenital adrenal hyperplasia is the name given to a group of inherited disorders of the adrenal gland. adrenal gland

Diseases & Conditions
Congenital antithrombin III deficiency
Congenital antithrombin III deficiency is a genetic disorder that causes the blood to clot more than normal. genetic

Diseases & Conditions
Congenital fibrinogen deficiency
Congenital fibrinogen deficiency is a very rare, inherited blood disorder in which the blood does not clot normally. It affects a protein called fibrinogen. This protein is needed for the blood to clot...

Diseases & Conditions
Congenital heart disease
Congenital heart disease (CHD) is a problem with the heart's structure and function that is present at birth.

Diseases & Conditions
Congenital platelet function defects
Congenital platelet function defects are conditions that prevent clotting elements in the blood, called platelets, from working as they should. Platelets help the blood clot. Congenital means present from...

Diseases & Conditions
Congenital protein C or S deficiency
Congenital protein C or S deficiency is a lack of proteins C or S in the fluid part of the blood. The proteins are natural substances that help prevent blood clots.

Diseases & Conditions
Cri du chat syndrome
Cri du chat syndrome is a group of symptoms that result from missing a piece of chromosome number 5. The syndrome's name is based on the infant's cry, which is high-pitched and sounds like a cat. chromosome

Diseases & Conditions
Crigler-Najjar syndrome
Crigler-Najjar syndrome is a very rare inherited disorder in which bilirubin cannot be broken down. Bilirubin is a substance made by the liver.

Nutrition
Cystic fibrosis - nutrition
Cystic fibrosis (CF) is a life-threatening disease that causes thick, sticky mucus to build up in the lungs and digestive tract. People with CF need to eat foods that are high in calories and protein throughout...

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Diseases & Conditions
Dehydration
Dehydration occurs when your body does not have as much water and fluids as it needs. Dehydration can be mild, moderate, or severe, based on how much of your body's fluid is lost or not replaced. Severe...

Diseases & Conditions
Down syndrome
Down syndrome is a genetic condition in which a person has 47 chromosomes instead of the usual 46. chromosomes

Diseases & Conditions
Duchenne muscular dystrophy
Duchenne muscular dystrophy is an inherited muscular disease. It involves muscle weakness, which quickly gets worse. muscle weakness

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Symptoms
Earlobe creases
Earlobe creases are lines in the surface of earlobe of a child or young adult. The surface is otherwise smooth.

Diseases & Conditions
Ehlers-Danlos syndrome
Ehlers-Danlos syndrome (EDS) is a group of inherited disorders marked by extremely loose joints, very stretchy (hyperelastic) skin that bruises easily, and easily damaged blood vessels. hyperelastic

Diseases & Conditions
Ellis-van Creveld syndrome
Ellis-van Creveld syndrome is a rare genetic disorder that affects bone growth.

Special Topics
Enzyme markers
Enzyme markers are tests for specific enzyme activity in the body. Diseases or defects passed down through families (inherited) can affect how enzymes work. Some enzymes are affected by several genes. enzyme...

Diseases & Conditions
Essential thrombocythemia
Essential thrombocythemia (ET) is a condition in which the bone marrow produces too many platelets. Platelets are a part of the blood that aids in blood clotting.

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Diseases & Conditions
Facioscapulohumeral muscular dystrophy
Facioscapulohumeral muscular dystrophy is a muscle weakness and loss of muscle tissue that gets worse over time. muscle weakness

Diseases & Conditions
Factor V deficiency
Factor V deficiency is a bleeding disorder that is passed down through families. It affects the ability of the blood to clot. bleeding disorder

Diseases & Conditions
Factor VII deficiency
Factor VII (seven) deficiency is a disorder caused by a lack of a protein called factor VII in the blood. It leads to problems with blood clotting (coagulation).

Diseases & Conditions
Factor X deficiency
Factor X (ten) deficiency is a disorder caused by a lack of a protein called factor X in the blood. It leads to problems with blood clotting (coagulation).

Diseases & Conditions
Factor XII (Hageman factor) deficiency
Factor XII deficiency is an inherited disorder that affects a protein (factor XII) involved in blood clotting.

Diseases & Conditions
Familial Mediterranean fever
Familial Mediterranean fever (FMF) is a rare disorder passed down through families (inherited). It involves repeated fevers and inflammation that often affects the lining of the abdomen, chest, or joints...

Diseases & Conditions
Familial combined hyperlipidemia
Familial combined hyperlipidemia is a disorder that is passed down through families. It causes high cholesterol and high blood triglycerides. high blood triglycerides

Diseases & Conditions
Familial dysautonomia
Familial dysautonomia (FD) is an inherited disorder that affects nerves throughout the body.

Diseases & Conditions
Familial dysbetalipoproteinemia
Familial dysbetalipoproteinemia is a disorder passed down through families. It causes high amounts of cholesterol and triglycerides in the blood.

Diseases & Conditions
Familial hypercholesterolemia
Familial hypercholesterolemia is a disorder that is passed down through families. It causes LDL (bad) cholesterol level to be very high. The condition begins at birth and can cause heart attacks at an early...

Diseases & Conditions
Familial hypertriglyceridemia
Familial hypertriglyceridemia is a common disorder passed down through families. It causes a higher-than-normal level of triglycerides (a type of fat) in a person's blood.

Diseases & Conditions
Familial lipoprotein lipase deficiency
Familial lipoprotein lipase deficiency is a group of rare genetic disorders in which a person lacks a protein needed to break down fat molecules. The disorder causes a large amount of fat to build up in...

Diseases & Conditions
Fanconi anemia
Fanconi anemia is a rare disease passed down through families (inherited) that mainly affects the bone marrow. It results in decreased production of all types of blood cells. This is the most common inherited...

Diseases & Conditions
Fanconi syndrome
Fanconi syndrome is a disorder of the kidney tubes in which certain substances normally absorbed into the bloodstream by the kidneys are released into the urine instead.

Diseases & Conditions
Fibrous dysplasia
Fibrous dysplasia is a bone disease that destroys and replaces normal bone with fibrous bone tissue. One or more bones can be affected.

Diseases & Conditions
Fragile X syndrome
Fragile X syndrome is a genetic condition involving changes in part of the X chromosome. It is the most common form of inherited intellectual disability in boys. intellectual disability

Diseases & Conditions
Friedreich ataxia
Friedreich ataxia is a rare disease passed down through families (inherited). It affects the muscles and heart.

Symptoms
Frontal bossing
Frontal bossing is an unusually prominent forehead. It is sometimes associated with a heavier than normal brow ridge.

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Tests
Galactose-1-phosphate uridyltransferase blood test
Galactose-1-phosphate uridyltransferase is a blood test that measures the level of a substance called GALT, which helps break down milk sugars in your body. A low level of this substance causes a condition...

Diseases & Conditions
Galactosemia
Galactosemia is a condition in which the body is unable to use (metabolize) the simple sugar galactose. metabolize

Diseases & Conditions
Gastroschisis
Gastroschisis is a birth defect in which an infant's intestines are outside of the body because of a hole in the abdominal wall.

Diseases & Conditions
Gaucher disease
Gaucher disease is a rare genetic disorder in which a person lacks an enzyme called glucocerebrosidase (GBA).

Special Topics
Genes
A gene is a short piece of DNA. Genes tell the body how to build specific proteins. There are about 20,000 genes in each cell of the human body. Together, they make up the blueprint for the human body and...

Special Topics
Genetics
Genetics is the study of heredity, the process of a parent passing certain genes to their children. A person's appearance -- height, hair color, skin color, and eye color -- is determined by genes. Other...

Special Topics
Gestational age
Gestation is the period of time between conception and birth. During this time, the baby grows and develops inside the mother's womb. Gestational age is the common term used during pregnancy to describe...

Diseases & Conditions
Glanzmann thrombasthenia
Glanzmann thrombasthenia is a rare disorder of blood platelets. Platelets are a part of the blood that aids in blood clotting. platelets

Diseases & Conditions
Glucose-6-phosphate dehydrogenase deficiency
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a condition in which red blood cells break down when the body is exposed to certain drugs or the stress of infection. It is hereditary, which means...

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Diseases & Conditions
Hartnup disorder
Hartnup disorder is a genetic condition in which there is a defect in the transport of certain amino acids (such as tryptophan and histidine) by the small intestine and kidneys. amino acids tryptophan

Diseases & Conditions
Hemochromatosis
Hemochromatosis is a condition in which there is too much iron in the body. It is also called iron overload.

Diseases & Conditions
Hemoglobin C disease
Hemoglobin C disease is a blood disorder passed down through families. It leads to a type of anemia, which occurs when red blood cells break down earlier than normal. anemia

Diseases & Conditions
Hemoglobinopathy
Hemoglobinopathy is a group of disorders in which there is abnormal production or structure of the hemoglobin molecule. It is passed down through families (inherited). hemoglobin This group of disorders...

Diseases & Conditions
Hemophilia
Hemophilia refers to a group of bleeding disorders in which blood clotting takes a long time. There are two forms of hemophilia: Hemophilia A (classic hemophilia, or factor VIII deficiency)Hemophilia B...

Diseases & Conditions
Hemophilia A
Hemophilia A is a hereditary bleeding disorder caused by a lack of blood clotting factor VIII. Without enough factor VIII, the blood cannot clot properly to control bleeding. bleeding disorder

Diseases & Conditions
Hemophilia B
Hemophilia B is a hereditary bleeding disorder caused by a lack of blood clotting factor IX. Without enough factor IX, the blood cannot clot properly to control bleeding.

Diseases & Conditions
Hereditary amyloidosis
Hereditary amyloidosis is a condition in which abnormal protein deposits (called amyloid) form in almost every tissue in the body. Harmful deposits most often form in the heart, kidneys, and nervous system...

Diseases & Conditions
Hereditary elliptocytosis
Hereditary elliptocytosis is a disorder passed down through families in which the red blood cells are abnormally shaped. It is similar to other blood conditions such as hereditary spherocytosis and hereditary...

Diseases & Conditions
Hereditary fructose intolerance
Hereditary fructose intolerance is a disorder in which a person lacks the protein needed to break down fructose. Fructose is a fruit sugar that naturally occurs in the body. Man-made fructose is used as...

Diseases & Conditions
Hereditary hemorrhagic telangiectasia
Hereditary hemorrhagic telangiectasia (HHT) is an inherited disorder of the blood vessels that can cause excessive bleeding.

Diseases & Conditions
Hereditary ovalocytosis
Hereditary ovalocytosis is a rare condition passed down through families (inherited). The blood cells are oval-shaped instead of round. It is a form of hereditary elliptocytosis. hereditary elliptocytosis

Diseases & Conditions
Hereditary spherocytic anemia
Hereditary spherocytic anemia is a rare disorder of the surface layer (membrane) of red blood cells. It leads to red blood cells that are shaped like spheres, and premature breakdown of red blood cells...

Diseases & Conditions
Hereditary urea cycle abnormality
Hereditary urea cycle abnormality is an inherited condition. It can cause problems with the removal of waste from the body in the urine.

Diseases & Conditions
Hirschsprung disease
Hirschsprung disease is a blockage of the large intestine. It occurs due to poor muscle movement in the bowel. It is a congenital condition, which means it is present from birth.

Diseases & Conditions
Homocystinuria
Homocystinuria is a genetic disorder that affects the metabolism of the amino acid methionine. Amino acids are the building blocks of life. metabolism amino acid

Diseases & Conditions
Huntington disease
Huntington disease (HD) is a genetic disorder in which nerve cells in certain parts of the brain waste away, or degenerate. The disease is passed down through families.

Diseases & Conditions
Hyperimmunoglobulin E syndrome
Hyperimmunoglobulin E syndrome is a rare, inherited disease. It causes problems with the skin, sinuses, lungs, bones, and teeth.

Symptoms
Hypotonia
Hypotonia means decreased muscle tone.

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Nutrition
Inborn errors of metabolism
Inborn errors of metabolism are rare genetic (inherited) disorders in which the body cannot properly turn food into energy. The disorders are usually caused by defects in specific proteins (enzymes) that...

Special Topics
Infant test/procedure preparation
Being prepared before your infant has a medical test can help you know what to expect during the test. It will also help reduce your anxiety so that you can help keep your infant as calm and comfortable...

Diseases & Conditions
Intersex
Intersex is a group of conditions where there is a discrepancy between the external genitals and the internal genitals (the testes and ovaries). The older term for this condition is hermaphroditism. Although...

K

Tests
Karyotyping
Karyotyping is a test to examine chromosomes in a sample of cells. This test can help identify genetic problems as the cause of a disorder or disease.

Diseases & Conditions
Klinefelter syndrome
Klinefelter syndrome is a genetic condition that occurs in males when they have an extra X chromosome.

Diseases & Conditions
Klippel-Trenaunay syndrome
Klippel-Trenaunay syndrome (KTS) is a rare condition that is typically present at birth. The syndrome often involves port wine stains, excess growth of bones and soft tissue, and varicose veins.

Diseases & Conditions
Krabbe disease
Krabbe disease is a rare genetic disorder of the nervous system. It is a type of brain disease called leukodystrophy.

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Diseases & Conditions
Limb-girdle muscular dystrophies
Limb-girdle muscular dystrophies include at least 18 different inherited diseases. (There are 16 known genetic forms. ) These disorders first affect the muscles around the shoulder girdle and hips. These...

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Special Topics
Macroglossia
Macroglossia is a disorder in which the tongue is larger than normal.

Diseases & Conditions
Malignant hyperthermia
Malignant hyperthermia (MH) is a disease that causes a fast rise in body temperature and severe muscle contractions when someone with MH gets general anesthesia. MH is passed down through families. general...

Diseases & Conditions
Maple syrup urine disease
Maple syrup urine disease (MSUD) is a disorder in which the body cannot break down certain parts of proteins. The urine of people with this condition can smell like maple syrup.

Diseases & Conditions
Marfan syndrome
Marfan syndrome is a disorder of connective tissue. This is the tissue that strengthens the body's structures. Disorders of connective tissue affect the skeletal system, cardiovascular system, eyes, and...

Diseases & Conditions
McCune-Albright syndrome
McCune-Albright syndrome is a genetic disease that affects the bones, hormones, and color (pigmentation) of the skin.

Diseases & Conditions
Menkes disease
Menkes disease is an inherited disorder in which the body has a problem absorbing copper. The disease affects development, both mental and physical.

Diseases & Conditions
Metachromatic leukodystrophy
Metachromatic leukodystrophy (MLD) is a genetic disorder that affects nerves, muscles, other organs, and behavior. It slowly gets worse over time.

Tests
Methylene blue test
The methylene blue test is a test to determine the type or to treat methemoglobinemia, a blood disorder. methemoglobinemia

Symptoms
Microcephaly
Microcephaly is a condition in which a person's head size is much smaller than that of others of the same age and sex. Head size is measured as the distance around the top of the head. A smaller than normal...

Symptoms
Micrognathia
Micrognathia is a term for a lower jaw that is smaller than normal.

Diseases & Conditions
Mosaicism
Mosaicism is a condition in which cells within the same person have a different genetic makeup. This condition can affect any type of cell, including: Blood cellsEgg and sperm cells Skin cells Blood cells...

Special Topics
Mucopolysaccharides
Mucopolysaccharides are long chains of sugar molecules that are found throughout the body, often in mucus and in fluid around the joints. They are more commonly called glycosaminoglycans.

Diseases & Conditions
Mucopolysaccharidoses
Mucopolysaccharidoses (MPSs) are a group of rare diseases in which the body is missing or does not have enough of an enzyme needed to break down long chains of sugar molecules. These chains of molecules...

Diseases & Conditions
Mucopolysaccharidosis type I
Mucopolysaccharidosis type I (MPS I) is a rare disease in which the body is missing or does not have enough of an enzyme needed to break down long chains of sugar molecules. These chains of molecules are...

Diseases & Conditions
Mucopolysaccharidosis type II
Mucopolysaccharidosis type II (MPS II) is a rare disease in which the body is missing or does not have enough of an enzyme needed to break down long chains of sugar molecules. These chains of molecules...

Diseases & Conditions
Mucopolysaccharidosis type III
Mucopolysaccharidosis type III (MPS III) is a rare disease in which the body is missing or does not have enough of certain enzymes needed to break down long chains of sugar molecules. These chains of molecules...

Diseases & Conditions
Mucopolysaccharidosis type IV
Mucopolysaccharidosis type IV (MPS IV) is a rare disease in which the body is missing or does not have enough of an enzyme needed to break down long chains of sugar molecules. These chains of molecules...

N

Diseases & Conditions
Neurofibromatosis 2
Neurofibromatosis 2 (NF2) is a disorder in which tumors form on the nerves of the brain and spine (the central nervous system). It is passed down (inherited) in families. Although it has a similar name...

Diseases & Conditions
Neurofibromatosis-1
Neurofibromatosis-1 (NF1) is an inherited disorder in which nerve tissue tumors (neurofibromas) form in the: tumors Upper and lower layers of the skinNerves from the brain (cranial nerves) and spinal cord...

Diseases & Conditions
Neuronal ceroid lipofuscinoses (NCL)
Neuronal ceroid lipofuscinoses (NCL) refers to a group of rare disorders of the nerve cells. NCL is passed down through families (inherited). These are the three main types of NCL: Adult (Kufs or Parry...

Diseases & Conditions
Niemann-Pick disease
Niemann-Pick disease (NPD) is a group of diseases passed down through families (inherited) in which fatty substances called lipids collect in the cells of the spleen, liver, and brain. There are three common...

Tests
Nitroblue tetrazolium blood test
The nitroblue tetrazolium test checks if certain immune system cells can change a colorless chemical called nitroblue tetrazolium (NBT) into a deep blue color.

Diseases & Conditions
Noonan syndrome
Noonan syndrome is a disease present from birth (congenital) that causes many parts of the body to develop abnormally. In some cases it is passed down through families (inherited).

O

Diseases & Conditions
Omphalocele
An omphalocele is a birth defect in which an infant's intestine or other abdominal organs are outside of the body because of a hole in the belly button (navel) area. The intestines are covered only by a...

Diseases & Conditions
Osteogenesis imperfecta
Osteogenesis imperfecta is a condition causing extremely fragile bones.

P

Diseases & Conditions
Paroxysmal nocturnal hemoglobinuria (PNH)
Paroxysmal nocturnal hemoglobinuria is a rare disease in which red blood cells break down earlier than normal.

Diseases & Conditions
Partial androgen insensitivity syndrome
Partial androgen insensitivity syndrome (PAIS) is a disease that occurs in children when their body can't respond the right way to the male sex hormones (androgens). Testosterone is a male sex hormone....

Diseases & Conditions
Patent foramen ovale
Patent foramen ovale (PFO) is a hole between the left and right atria (upper chambers) of the heart. This hole exists in everyone before birth, but most often closes shortly after being born. PFO is what...

Diseases & Conditions
Peutz-Jeghers syndrome
Peutz-Jeghers syndrome (PJS) is a rare disorder in which growths called polyps form in the intestines. A person with PJS has a high risk of developing certain cancers.

Diseases & Conditions
Phenylketonuria
Phenylketonuria (PKU) is a rare condition in which a baby is born without the ability to properly break down an amino acid called phenylalanine.

Diseases & Conditions
Pierre Robin sequence
Pierre Robin sequence (or syndrome) is a condition in which an infant has a smaller than normal lower jaw, a tongue that falls back in the throat, and difficulty breathing. It is present at birth.

Diseases & Conditions
Polycythemia vera
Polycythemia vera (PV) is a bone marrow disease that leads to an abnormal increase in the number of blood cells. The red blood cells are mostly affected.

Symptoms
Polydactyly
Polydactyly is a condition in which a person has more than 5 fingers per hand or 5 toes per foot.

Diseases & Conditions
Porphyria
Porphyrias are a group of rare inherited disorders. An important part of hemoglobin, called heme, is not made properly. Hemoglobin is a protein in red blood cells that carries oxygen. Heme is also found...

Diseases & Conditions
Potter syndrome
Potter syndrome and Potter phenotype refers to a group of findings associated with a lack of amniotic fluid and kidney failure in an unborn infant. amniotic fluid kidney failure

Diseases & Conditions
Precocious puberty
Puberty is the time during which a person's sexual and physical characteristics mature. Precocious puberty is when these body changes happen earlier than normal.

Diseases & Conditions
Primary amyloidosis
Primary amyloidosis is a rare disorder in which abnormal proteins build up in tissues and organs. Clumps of the abnormal proteins are called amyloid deposits.

Diseases & Conditions
Progeria
Progeria is a rare genetic condition that produces rapid aging in children.

Diseases & Conditions
Prothrombin deficiency
Prothrombin deficiency is a disorder caused by a lack of a protein in the blood called prothrombin. It leads to problems with blood clotting (coagulation). Prothrombin is also known as factor II (factor...

Diseases & Conditions
Prune belly syndrome
Prune belly syndrome is a group of rare birth defects that involves these three main problems: Poor development of the abdominal muscles, causing the skin of the belly area to wrinkle like a pruneUndescended...

Diseases & Conditions
Pulmonary atresia
Pulmonary atresia is a form of heart disease in which the pulmonary valve does not form properly. It is present from birth (congenital heart disease). The pulmonary valve is an opening on the right side...

Diseases & Conditions
Pyruvate kinase deficiency
Pyruvate kinase deficiency is an inherited lack of the enzyme pyruvate kinase, which is used by red blood cells. Without this enzyme, red blood cells break down too easily, resulting in a low level of these...

R

Diseases & Conditions
Repeated nightmares
Repeated nightmares are bad dreams that recur frequently and involve the same theme. nightmares Nightmares usually begin before the age of 10. They are considered a normal part of childhood, unless they...

Diseases & Conditions
Rickets
Rickets is a disorder caused by a lack of vitamin D, calcium, or phosphate. It leads to softening and weakening of the bones.

Diseases & Conditions
Rubinstein-Taybi syndrome
Rubinstein-Taybi syndrome (RTS) is a genetic disease. It involves broad thumbs and toes, short stature, distinctive facial features, and varying degrees of intellectual disability.

Diseases & Conditions
Russell-Silver syndrome
Russell-Silver syndrome (RSS) is a disorder present at birth involving poor growth. One side of the body may also appear to be larger than the other.

S

Special Topics
Sex-linked dominant
Sex-linked dominant is a rare way that a trait or disorder can be passed down through families. One abnormal gene on the X chromosome can cause a sex-linked dominant disease. Related terms and topics include...

Special Topics
Sex-linked recessive
Sex-linked diseases are passed down through families through one of the X or Y chromosomes. X and Y are sex chromosomes. Dominant inheritance occurs when an abnormal gene from one parent causes disease...

Symptoms
Short philtrum
A short philtrum is a shorter than normal distance between the upper lip and the nose.

Diseases & Conditions
Sickle cell disease
Sickle cell disease is a disorder passed down through families. The red blood cells that are normally shaped like a disk take on a sickle or crescent shape. Red blood cells carry oxygen throughout the body...

Symptoms
Single palmar crease
A single palmar crease is a single line that runs across the palm of the hand. People most often have 3 creases in their palms. The crease is most often referred to as a single palmar crease. The older...

Special Topics
Skin findings in newborns
A newborn infant's skin goes through many changes both in appearance and texture.

Special Topics
Stem cell research
A stem cell is a generic cell that can make exact copies of itself indefinitely. A stem cell has the ability to make specialized cells for various tissues in the body, such as heart muscle, brain tissue...

Diseases & Conditions
Sturge-Weber syndrome
Sturge-Weber syndrome (SWS) is a rare disorder that is present at birth. A child with this condition will have a port-wine stain birthmark (usually on the face) and may have nervous system problems.

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Diseases & Conditions
Tay-Sachs disease
Tay-Sachs disease is a life-threatening disease of the nervous system passed down through families.

Diseases & Conditions
Testicular failure
Testicular failure occurs when the testicles cannot produce sperm or male hormones, such as testosterone. testicles

Diseases & Conditions
Thalassemia
Thalassemia is a blood disorder passed down through families (inherited) in which the body makes an abnormal form or inadequate amount of hemoglobin. Hemoglobin is the protein in red blood cells that carries...

Diseases & Conditions
Total anomalous pulmonary venous return
Total anomalous pulmonary venous return (TAPVR) is a heart disease in which the 4 veins that take blood from the lungs to the heart do not attach normally to the left atrium (left upper chamber of the heart...

Diseases & Conditions
Transient familial hyperbilirubinemia
Transient familial hyperbilirubinemia is a metabolic disorder that is passed down through families. Babies with this disorder are born with severe jaundice. jaundice

Special Topics
Translocation
Translocation means a change in location. It often refers to genetics, when part of a chromosome is transferred to another chromosome. Chromosomes are structures that carry genes, our units of heredity...

Diseases & Conditions
Treacher Collins syndrome
Treacher Collins syndrome is a genetic condition that leads to problems with the structure of the face. Most cases are not passed down through families.

Diseases & Conditions
Tricuspid atresia
Tricuspid atresia is a type of heart disease that is present at birth (congenital heart disease), in which the tricuspid heart valve is missing or abnormally developed. The defect blocks blood flow from...

Diseases & Conditions
Trisomy 13
Trisomy 13 (also called Patau syndrome) is a genetic disorder in which a person has 3 copies of genetic material from chromosome 13, instead of the usual 2 copies. Rarely, the extra material may be attached...

Diseases & Conditions
Trisomy 18
Trisomy 18 is a genetic disorder in which a person has a third copy of material from chromosome 18, instead of the usual 2 copies. Most cases are not passed down through families. Instead, the problems...

Diseases & Conditions
Tuberous sclerosis
Tuberous sclerosis is a genetic disorder that affects the skin, brain/nervous system, kidneys, heart, and lungs. The condition can also cause tumors to grow in the brain. These tumors have a tuber or root...

Diseases & Conditions
Turner syndrome
Turner syndrome is a rare genetic condition in which a female does not have the usual pair of X chromosomes.

Diseases & Conditions
Type V glycogen storage disease
Type V (five) glycogen storage disease (GSD V) is a rare inherited condition in which the body is not able to break down glycogen. Glycogen is an important source of energy that is stored in all tissues...

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Diseases & Conditions
Von Willebrand disease
Von Willebrand disease is the most common hereditary bleeding disorder. bleeding disorder

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Diseases & Conditions
Waardenburg syndrome
Waardenburg syndrome is a group of conditions passed down through families. The syndrome involves deafness and pale skin, hair, and eye color. deafness

Diseases & Conditions
Williams syndrome
Williams syndrome is a rare disorder that can lead to problems with development.

Diseases & Conditions
Wilson disease
Wilson disease is an inherited disorder in which there is too much copper in the body's tissues. The excess copper damages the liver and nervous system.

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Diseases & Conditions
von Gierke disease
Von Gierke disease is a condition in which the body cannot break down glycogen. Glycogen is a form of sugar (glucose) that is stored in the liver and muscles. It is normally broken down into glucose to...