Browse plain-English disease and condition guides, including symptoms, causes, diagnosis, treatment options, prevention, and when to seek medical care.
Anal Anomalies–Porokeratosis Syndrome, often referred to as AAPS, is a rare medical condition that affects various aspects of a person’s health. In this comprehensive article, we...
Read article11β-HSD2 deficiency is a rare genetic condition in which the body cannot properly switch the hormone cortisol into its inactive form, cortisone, inside certain kidney cells....
Read article1p36 microdeletion syndrome (also called 1p36 deletion syndrome) is a genetic condition that starts before birth. A small piece of chromosome 1, from the short arm...
Read article1q21.1 deletion syndrome (also called 1q21.1 microdeletion) is a genetic disorder caused by the loss of a small segment of DNA on the long arm (q...
Read article1q21.1 duplication syndrome (also called 1q21.1 microduplication) is a chromosomal copy-number variant in which a small segment of genetic material on the long (q) arm of...
Read article1q21.1 recurrent microdeletion is a tiny missing piece of DNA on chromosome 1, at a place called “1q21.1.” In this condition, one copy of chromosome 1...
Read article2-methylacyl-CoA racemase deficiency is a very rare inherited metabolic disease. It happens when the body does not make enough working AMACR enzyme. This enzyme helps break...
Read article2,8-dihydroxyadenine (DHA) urolithiasis is a rare form of kidney stone disease. It happens when the body cannot recycle the purine base adenine in the normal “salvage”...
Read article2,8-dihydroxyadeninuria is a rare, inherited problem of purine recycling. Your body normally reuses adenine (a building block of DNA) using an enzyme called APRT (adenine phosphoribosyltransferase)....
Read article21-hydroxylase-deficient congenital adrenal hyperplasia (CAH) is a genetic disease that affects how the adrenal glands make important hormones called cortisol and aldosterone. The adrenal glands are...
Read article3-beta-hydroxy-delta-5-c27-steroid dehydrogenase deficiency is a very rare inherited liver disease. It is one of the bile acid synthesis disorders. In this condition, the liver cannot make...
Read article3-methylglutaconic aciduria type 2 is a rare, inherited condition that almost always affects boys. It is also called Barth syndrome. It happens because of a change...
Read articleArterial tortuosity syndrome (ATS) is an extremely rare genetic congenital connective tissue disorder characterized by lengthening (elongation) and twisting or distortion (tortuosity) of major arteries with...
Read articleAromatic l-amino acid decarboxylase (AADC) deficiency is a very rare genetic autosomal recessive neurometabolic disorder that leads to a severe combined deficiency of serotonin, dopamine, norepinephrine,...
Read articleArgininosuccinic aciduria is a rare genetic disorder characterized by the deficiency or lack of the enzyme argininosuccinate lyase (ASL). This enzyme is one of six enzymes...
Read articleGlycine amidinotransferase deficiency (AGAT) is one of the three cerebral creatine deficiency syndromes (CCDS). These conditions are inborn errors of creatine metabolism which interrupt the formation...
Read articleArginase-1 deficiency is a rare inherited autosomal recessive disorder causing hyperammonemia secondary to arginine accumulation characterized by a complete or partial lack of the enzyme arginase...
Read articleArachnoid cysts are fluid-filled sacs that occur on the arachnoid membrane that covers the brain (intracranial) and the spinal cord (spinal) majority of arachnoid cysts are...
Read articleApraxia is a neurological disorder as a non-motor abnormality characterized by the patient’s difficulty in eyelid elevation bilaterally inability of voluntary eye reopening without an orbicularis...
Read articleCancers and tumors (neoplasms) of the appendix are extremely rare groups of tumors and they most typically present either as appendicitis, a hernia filled with mucin,...
Read articleInfantile apnea is a rare disease that is characterized by cessation of breathing in an infant for at least 20 seconds or a shorter respiratory pause...
Read articleAplasia Cutis Congenita is a rare disorder with a complicated pattern of inheritance congenital skin defect characterized by a focal or extensive absence of the epidermis,...
Read articleApert syndrome is a rare autosomal dominant inherited craniosynostosis genetic condition that is apparent at birth through the premature fusion of coronal sutures resulting in the...
Read articleAP-4-associated hereditary spastic paraplegia (AP-4-HSP) is a group of slowly-progressing neurodegenerative disorders that generally present with global developmental delay, moderate to severe intellectual disability, impaired/absent speech,...
Read articleAntley-Bixler syndrome is a rare genetic disorder that can cause structural changes to the skull, bones of the face, and other skeletal abnormalities. It is a...
Read articleAntithrombin deficiency is a blood disorder characterized by the tendency to form clots in the veins (thrombosis). An inherited tendency to thrombosis is known as thrombophilia....
Read articleAntisynthetase syndrome is a rare, chronic, autoimmune disorder characterized by Interstitial Lung Disease (ILD), inflammatory myositis, fever, Raynaud’s phenomenon, mechanic’s hand, and inflammatory polyarthritis in the...
Read articleAntiphospholipid syndrome (APS) is a rare autoimmune multisystemic disorder characterized by the presence of antiphospholipid antibodies in the setting of thrombosis and/or pregnancy loss and the most...
Read articleGillespie syndrome, also known as Aniridia, cerebellar ataxia, and mental deficiency, is an extremely rare inherited disorder that is characterized by the absence, in whole (aniridia)...
Read articleAniridia, cerebellar ataxia, and mental deficiency, also known as Gillespie syndrome, is an extremely rare inherited disorder that is characterized by the absence, in whole (aniridia)...
Read articleAniridia is a rare condition characterized by a progressive fibrotic membrane within the anterior chamber that occurs after ocular surgery or by abnormal development of the...
Read articleAngioimmunoblastic T-cell lymphoma (AITL, sometimes misspelled AILT, formerly known as angioimmunoblastic lymphadenopathy with dysproteinemia ) is a rare form of non-Hodgkin lymphoma, which is a group of related...
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