2-methyl-3-hydroxybutyric aciduria

2-methyl-3-hydroxybutyric aciduria is an inherited disorder in which the body cannot effectively process the amino acid isoleucine. Signs and symptoms of this condition usually develop in infancy or early childhood and include metabolic acidosis, hypoglycemia, hypotonia, seizures, movement problems, retinal degeneration, and hearing loss. Affected males have severe neurodegeneration with loss of developmental milestones, whereas females have mild to moderate developmental delay. 2-methyl-3-hydroxybutyric aciduria is caused by mutations in the HSD17B10 gene; it has an X-linked dominant pattern of inheritance.

3-methylcrotonyl-CoA carboxylase deficiency

3-methylcrotonyl-CoA carboxylase deficiency is an inherited condition in which the body is unable to breakdown the amino acid, leucine (a building block of protein). Some children with 3-MCC deficiency will begin developing signs and symptoms during infancy or early childhood; however, more recent studies suggest that many affected babies identified through newborn screening will never experience symptoms of the condition. 3-MCC deficiency may be associated with episodes of "metabolic crisis" in which affected people experience poor appetite, lack of energy, irritability, weakness, nausea and/or vomiting. If metabolic crises are untreated, the condition can lead to developmental delay, seizures, coma, and even death.  

AA amyloidosis

AA amyloidosis is a progressive and fatal condition that affects approximately 50,000 people in the United States, Europe and Japan with chronic inflammatory diseases, including rheumatoid arthritis, ankylosing spondylitis, juvenile rheumatoid arthritis, and Crohn's disease.

The disease also occurs in patients suffering from many other conditions ranging from chronic infections to inherited inflammatory diseases such as Familial Mediterranean Fever. The most common clinical presentation of AA amyloidosis is renal dysfunction. Involvement of the gastrointestinal system is also frequent and is usually manifested as chronic diarrhea, gastrointestinal bleeding, abdominal pain and malabsorption. Enlargement of the liver and the spleen may also occur in some patients. End-stage renal failure is the main cause of death in 40-60% of cases. The median survival time from diagnosis varies from 2 to 10 years depending on the stage of the disease at the time of diagnosis.

Source: BELLUS Health

Aagenaes syndrome

Aagenaes syndrome: A rare inherited birth abnormality involving underdeveloped lymph vessels which results in swollen legs and liver problems.

A syndrome characterised by congenital hypoplasia of lymph vessels, which causes lymphedema of the legs and recurrent cholestasis in infancy, and slow progress to hepatic cirrhosis and giant-cell hepatitis with fibrosis of the portal tracts1. The genetic cause is unknown, but it is autosomal recessively inherited and the gene is located to chromosome 15q1,2. A common feature of the condition is a generalised lymphatic anomaly, which may be indicative of the defect being lymphangiogenetic in origin1. The condition is particularly frequent in southern Norway, where more than half the cases are reported from, but is found in patients in other parts of Europe and the U.S.2. It is named after Oystein Aagenaes, a Norwegian paediatrician.

Aarskog-Scott syndrome

Aarskog syndrome is an inherited disease that affects a person's height, muscles, skeleton, genitals, and appearance of the face. Inherited means that it is passed down through families.

The syndrome is named for Dagfinn Aarskog, a Norwegian pediatrician and human geneticist who first described it in 1970, and for Charles I. Scott, Jr., an American medical geneticist who independently described the syndrome in 1971.

Aase syndrome

Aase syndrome is a rare inherited disorder characterized by anemia with some joint and skeletal deformities. Aase syndrome is thought to be an autosomal recessive inherited disorder. The genetic basis of the disease is not known. The anemia is caused by underdevelopment of the bone marrow, which is where blood cells are formed.

It is named after the American paediatricians Jon Morton Aase and David Weyhe Smith, who characterized it in 1968.

ABCD syndrome

ABCD syndrome is a rare inherited condition. It has been found to be caused by mutation in the endothelin B receptor gene (EDNRB). This helped scientists discover that it is the same as type IV Waardenburg syndrome, also known as Shah-Waardenburg Syndrome.

Abderhalden-Kaufmann-Lignac syndrome

Abderhalden-Kaufmann-Lignac syndromeia a rare inherited childhood disorder involving deposits of cystine crystals in various parts of the body, especially the conjunctiva and cornea.

Abdominal aortic aneurysm

Abdominal aortic aneurysms are aneurysms that occur in the part of the aorta that passes through the abdomen. They may occur at any age, but are most common in men between 50 and 80 years of age. A localized widening or bulging of the abdominal aorta which is a major blood carrying vessel. A rupture of the weakened bulge is considered very serious because of the large volume of blood carried by this vessel. Many people with an AAA have no symptoms, but some people have a pulsing sensation in the abdomen and/or pain in the back. If the aneurysm ruptures, it may cause deep, severe pain; nausea; vomiting; fast heart rate; clammy skin; and/or shock. About 20% of AAAs eventually rupture and are often fatal. The condition has multiple genetic and environmental risk factors, and may sometimes occur as part of an inherited syndrome. When more than one family member is affected, it may be considered "familial abdominal aortic aneurysm." Treatment depends on the size of the aneurysm and may include blood pressure medications, or surgery to repair the aneurysm.

Abdominal cystic lymphangioma

Abdominal cystic lymphangioma ia a rare form of benign tumor that occurs in infants. It is essentially a malformation of one of the abdominal lymph vessels where a portion is dilated and form a lymph fluid-filled cyst. Symptoms may vary depending on the exact location and size of the cyst.

Abdominal obesity metabolic syndrome

Abdominal obesity metabolic syndrome is a syndrome characterized by a group of conditions that are considered major risk factors for diabetes mellitus and cardiovascular disease.

Aberrant subclavian artery

Aberrant subclavian artery is a rare vascular anomaly that is present from birth. It usually causes no symptoms and is often discovered as an incidental finding (such as through a barium swallow or echocardiogram). Occasionally the anomaly causes swallowing difficulty (dysphagia lusoria). One the subclavian artery arises from an abnormal location on the aortic arch. The defect may cause compression of organs such as the airway and the voice box. Swallowing symptoms in children may present as feeding difficulty and/or recurrent respiratory tract infection. When aberrant subclavian artery causes no symptoms, treatment is not needed. If the anomaly is causing significant symptoms, treatment may involve surgery. Children with symptomatic aberrant subclavian artery should be carefully evaluated for additional vascular and heart anomalies.


Abetalipoproteinemia is a condition characterized by the inability to fully absorb dietary fats, cholesterol and fat-soluble vitamins. The resulting insufficiency of fats and vitamins affect the normal development and function of the body. Signs and symptoms appear in the first few months of life and can include failure to thrive; diarrhea; acanthocytosis; and stool abnormalities. Other features develop later in childhood and often impair the function of the nervous system, potentially causing slower intellectual development; poor muscle coordination; progressive ataxia; and an eye disorder called retinitis pigmentosa. Most of the symptoms are due to defects in the absorption and transport of vitamin E. Abetalipoproteinemia is caused by mutations in the MTTP gene and is inherited in an autosomal recessive manner. Early diagnosis, high-dose vitamin E therapy, and medium-chain fatty acid supplements may slow the progression of the nervous system abnormalities. Long-term outlook is reasonably good for most affected people who are diagnosed early. If left untreated, the condition can result in early death.

Ablepharon macrostomia syndrome

Ablepharon Macrostomia Syndrome is an extremely rare inherited genetic disorder that is characterized by different physical abnormalities that affect the head and facial areas, skin, fingers, and the genitalia. The people affected by AMS may also have malformations of the nipples and the abdominal wall. Younger individuals might experience language difficulties, and in some instances mental retardation is known.

Abrikosov’s tumor

Abrikosov's tumor (medical condition) is a rare condition characterized by superficial, usually benign, slow-growing tumors occurring mostly on oral and genital tract tissue but occurs on the tongue 40% of the time.

Abruzzo Erickson syndrome

Abruzzo-Erickson syndrome (medical condition) is an extremely rare condition characterized by cleft palate, coloboma, hypospadius, deafness, short stature, and radioulnar synostosis. Treatment is generally aimed at addressing the symptoms present in each individual.

Absence defect of limbs, scalp and skull

Adams-Oliver Syndrome is a very rare inherited disorder characterized by scalp, skull and limb abnormalities. The range and severity of the symptoms can vary greatly from mild to severe.

Absence of Gluteal muscle

Absence of gluteal muscle: The absence of the buttock (gluteal) muscles at birth. Spina bifida occulta (absence of back part of some vertebrae) was also present.

Absence of septum pellucidum

Absence of septum pellucidum (medical condition) is the absence of the thin membrane that separates the two halves of the brain. The defect itself is not a disorder but is usually observed as a characteristic of a condition called septo-optic dysplasia which also involves optic nerve and pituitary abnormalities.

Absence of Tibia

Absence of tibia is a rare birth defect that is characterized by deficiency of the tibia (the shinbone) with other bones of the lower leg relatively intact. The condition may affect one or both legs. Some cases are isolated birth defects, while others are associated with a variety of skeletal and other malformations. It can also be a part of a recognized syndrome such as Werner's syndrome, tibial hemimelia-polysyndactyly-triphalangeal thumb syndrome, and CHARGE syndrome. 

Absence of tibia with polydactyly

Absence of tibia with polydactyly is the congenital absence of the tibial bone which is the shin bone as well as the presence of extra fingers.

Absent corpus callosum cataract immunodeficiency

Absent corpus callosum - cataract - immunodeficiency is a rare syndrome characterized by immunodeficiency, cleft lip or palate, cataract, reduced pigmentation and brain abnormalities.

Vici syndrome is a multisystem disorder characterized by agenesis (failure to develop) of the corpus callosum, cataracts , hypopigmentation of the eyes and hair, cardiomyopathy, and combined immunodeficiency. Hearing loss, seizures, and delayed motor development have also been reported. Swallowing and feeding difficulties early on may result in a failure to thrive. Recurrent infections of the respiratory, gastrointestinal, and urinary tracts are common. Vici syndrome is caused by mutations in the EPG5 gene and is inherited in an autosomal recessive manner. Treatment is mainly supportive.

Absent duct of Santorini

The pancreatic duct allows movement of pancreatic juices between the pancreas and common bile duct. Only some people have an additional accessory pancreatic duct called the Duct of Santorini. Generally the anomaly is asymptomatic but some patients may have an increased risk of developing pancreatitis due to other associated ductal anomalies.

Absent patella

A rare genetic malformation where the kneecap is absent or reduced.

Abuse dwarfism syndrome

Abuse dwarfism syndrome: Retarded growth, intelligence and social behavior due to child abuse. The child abuse can take the form of mental or physical cruelty or neglect.


Acalvaria is a rare malformation consisting of absence of the calvarial bones, dura mater and associated muscles in the presence of a normal skull base and normal facial bones. The skull base and facial features are fully formed and usually appear normal.The central nervous system is usually unaffected. The presumed pathogenesis of acalvaria is faulty migration of the membranous neurocranium with normal placement of the embryonic ectoderm, resulting in absence of the calvaria but an intact layer of skin over the brain parenchyma. In other words, instead of having a skull cap protecting the brain, there is only skin covering it. The size of the area that is missing the skull cap can vary from case to case. In extreme cases, the entire top part of the cranium that is dome-shaped may be absent.

The cause of acalvaria is still unknown. Acalvaria can be distinguished from anencephaly, the most common differential diagnosis, by the presence of a layer of skin overlying the brain matter and normal cerebral hemispheres. This malformation is most often lethal at birth due to other associated anomalies or to trauma during delivery, but a few surviving infants have been reported. Prenatal diagnosis via transvaginal ultrasound and/or magnetic resonance imaging is critical for better pregnancy management.

Acanthamoeba infection

Acanthamoeba infection is a cutaneous condition resulting from Acanthamoeba that may result in various skin lesions. Acanthamoeba strains can also infect human eyes causing acanthamoebic keratitis. Acanthamoeba are microscopic amoeba commonly found in the environment.

Several species of Acanthamoeba have been found to infect humans;

  • A. culbertsoni
  • A. polyphaga
  • A. castellanii
  • A. healyi
  • A. astronyxis
  • A. hatchetti
  • A. rhysodes

and possibly others.