- Aarskog syndrome
- Aase syndrome
- Abetalipoproteinemia
- Acardia
- Accutane embryopathy
- Achondrogenesis
- Achondroplasia
- ACHOO syndrome
- Acid maltase deficiency
- Acrocallosal syndrome
- Acromegaly
- Adams-Oliver syndrome
- Adrenoleukodystrophy
- Aicardi syndrome
- Alagille syndrome
- Albinism
- Alcoholism
- Alkaptonuria
- Alpha-1 antitrypsin
- Alzheimer disease
- Amelia
- Amniocentesis
- Amyotrophic lateral sclerosis
- Androgen insensitivity syndrome
- Anemia, sideroblastic X-linked
- Anencephaly
- Angelman syndrome
- Ankylosing spondylitis
- Apert syndrome
- Arginase deficiency
