·     A-T see ataxia-telangiectasia

·     AAT see alpha-1 antitrypsin deficiency

·     Absence of vas deferens see congenital bilateral absence of vas deferens

·     Absent vasa see congenital bilateral absence of vas deferens

·     ACADM deficiency see medium-chain acyl-coenzyme A dehydrogenase deficiency

·     ACADVL see very long-chain acyl-coenzyme A dehydrogenase deficiency

·     ACG1B see achondrogenesis, type 1B

·     ACG2 see achondrogenesis, type 2

·     ACH see achondroplasia

·     achondrogenesis, type 1B

·     achondrogenesis, type 2

·     achondroplasia

·     Acid beta-glucosidase deficiency see Gaucher disease, type 1

·     Acrocephalosyndactyly (Apert) see Apert syndrome

·     acrocephalosyndactyly, type V see Pfeiffer syndrome

·     Acrocephaly see Apert syndrome

·     Acute cerebral Gaucher's disease see Gaucher disease, type 2

·     acute intermittent porphyria

·     ACY2 deficiency see Canavan disease

·     acyl-CoA dehydrogenase very long chain deficiency see very long-chain acyl-coenzyme A dehydrogenase deficiency

·     AD see Alzheimer disease

·     Adelaide-type craniosynostosis see Muenke syndrome

·     Adenomatous Polyposis Coli see familial adenomatous polyposis

·     Adenomatous Polyposis of the Colon see familial adenomatous polyposis

·     ADP see ALAD deficiency porphyria

·     Adrenal Gland Disorders see 21-hydroxylase deficiency

·     Adrenogenital Syndrome see 21-hydroxylase deficiency

·     AIP see acute intermittent porphyria

·     AIS see androgen insensitivity syndrome

·     AKU see alkaptonuria

·     5-ALA dehydratase-deficient porphyria see ALAD deficiency porphyria

·     ALA-D porphyria see ALAD deficiency porphyria

·     ALA dehydratase porphyria see ALAD deficiency porphyria

·     ALAD deficiency porphyria

·     Alagille syndrome

·     Alcaptonuria see alkaptonuria

·     Alexander disease

·     alkaptonuria

·     Alkaptonuric ochronosis see alkaptonuria

·     alpha-1 antitrypsin deficiency

·     Alpha-galactosidase A deficiency see Fabry disease

·     alpha-1 proteinase inhibitor see alpha-1 antitrypsin deficiency

·     alpha-1 related emphysema see alpha-1 antitrypsin deficiency

·     Alport syndrome

·     ALS see amyotrophic lateral sclerosis

·     Alström syndrome

·     ALX see Alexander disease

·     Alzheimer disease

·     Alzheimer's Caregivers see Alzheimer disease

·     Alzheimer's Disease see Alzheimer disease

·     Amino levulinic acid dehydratase deficiency see ALAD deficiency porphyria

·     Aminoacylase 2 deficiency see Canavan disease

·     5-aminolaevulinic dehydratase deficiency porphyria see ALAD deficiency porphyria

·     amyotrophic lateral sclerosis

·     Andersen cardiodysrhythmic periodic paralysis see Andersen-Tawil syndrome

·     Andersen syndrome see Andersen-Tawil syndrome

·     Andersen-Tawil syndrome

·     Anderson-Fabry Disease see Fabry disease

·     androgen insensitivity syndrome

·     Anemia

·     Anemia, hereditary sideroblastic see X-linked sideroblastic anemia

·     Anemia, sex-linked hypochromic sideroblastic see X-linked sideroblastic anemia

·     Anemia, splenic, familial see Gaucher disease

·     Angelman syndrome

·     Angiokeratoma Corporis Diffusum see Fabry disease

·     Angiokeratoma diffuse see Fabry disease

·     Angiomatosis retinae see von Hippel-Lindau syndrome

·     ANH1 see X-linked sideroblastic anemia

·     AO2 see atelosteogenesis, type 2

·     APC resistance, Leiden type see factor V Leiden thrombophilia

·     Apert syndrome

·     AR-CMT2 see Charcot-Marie-Tooth disease, type 2

·     AR deficiency see androgen insensitivity syndrome

·     Arachnodactyly see Marfan syndrome

·     Argininosuccinate lyase deficiency see argininosuccinic aciduria

·     argininosuccinic aciduria

·     argininosuccinyl-CoA lyase deficiency see argininosuccinic aciduria

·     arginosuccinase deficiency see argininosuccinic aciduria

·     ARNSHL see nonsyndromic deafness, autosomal recessive

·     Arrhythmia

·     Arteriohepatic Dysplasia see Alagille syndrome

·     Arthro-ophthalmopathy, hereditary progressive see Stickler syndrome, COL2A1

·     Arthrochalasis multiplex congenita see Ehlers-Danlos syndrome, arthrochalasia type

·     AS see Angelman syndrome

·     ASL deficiency see argininosuccinic aciduria

·     Asp deficiency see Canavan disease

·     Aspa deficiency see Canavan disease

·     Aspartoacylase deficiency see Canavan disease

·     ataxia-telangiectasia

·     atelosteogenesis, type 2

·     ATS see Andersen-Tawil syndrome

·     Autism-Dementia-Ataxia-Loss of Purposeful Hand Use Syndrome see Rett syndrome

·     autosomal dominant juvenile ALS see amyotrophic lateral sclerosis, type 4

·     Autosomal dominant Opitz G/BBB syndrome see 22q11.2 deletion syndrome

·     autosomal recessive form of juvenile ALS type 3 see amyotrophic lateral sclerosis, type 2

·     Autosomal recessive nonsyndromic hearing loss see nonsyndromic deafness, autosomal recessive

·     Autosomal Recessive Sensorineural Hearing Impairment and Goiter see Pendred syndrome

·     AxD see Alexander disease

·     Ayerza Syndrome see primary pulmonary hypertension