- Cri du chat syndrome
- Crouzon syndrome
- Cystic fibrosis
- Cystinosis
- Cystinuria
- Dandy-Walker malformation
- Deletion 22q11 syndrome
- Dementia
- Dentatorubral-pallidoluysian atrophy
- Depression
- Diabetes
- Diastrophic dysplasia
- Distal arthrogryposis syndrome
- DNA (deoxyribonucleic acid)
- Donohue syndrome
- Down syndrome
- Duane retraction syndrome
- Dubowitz syndrome
- Duchenne muscular dystrophy
- Dysplasia
- Dystonia
- Ectodermal dysplasia
- Ehlers-Danlos syndrome
- Ellis-van Creveld syndrome
- Emery-Dreifuss muscular dystrophy
- Encephalocele
- Engelmann disease
- Epidermolysis bullosa
- Epilepsy
- Essential hypertension
