This is a list of diseases starting with the letter "N".

• N acetyltransferase deficiency
• N syndrome
• N-Acetylglutamate synthase deficiency
• N-acetyl-alpha-D-galactosaminidase
• N-acetyl-glucosamine-6-sulfate sulfatase deficiency
• NADH CoQ reductase, deficiency of
• NADH cytochrome B5 reductase deficiency
• Naegeli–Franceschetti–Jadassohn syndrome
• Naguib syndrome
• Nail–patella syndrome
• Nakajo–Nishimura syndrome
• Nakajo syndrome
• Nakamura–Osame syndrome
• NAME syndrome
• Nance–Horan syndrome
• Nanism due to growth hormone combined deficiency
• Nanism due to growth hormone isolated deficiency with X-linked hypogammaglobulinemia
• Nanism due to growth hormone resistance
• Narcissistic personality disorder
• Narcolepsy

• Narcolepsy-Cataplexy

• Narrow oral fissure short stature cone shaped epiphyses
• Nasodigitoacoustic syndrome
• Nasopalpebral lipoma coloboma syndrome
• Nasopharyngeal carcinoma
• Nasopharyngeal teratoma Dandy–Walker diaphragmatic hernia
• Nasopharyngitis

• Natal teeth intestinal pseudoobstruction patent ductus
• Nathalie syndrome
• Native American myopathy
• Navajo poikiloderma
• Naxos disease

• Nicolaides–Baraitser syndrome
• Nicotine withdrawal
• Niemann–Pick disease

• Niemann–Pick C1 disease
• Niemann–Pick C2 disease
• Niemann–Pick disease, type C
• Niemann-Pick disease type D

• Night blindness

• Night blindness skeletal anomalies unusual facies
• Night blindness, congenital stationary

• Nijmegen breakage syndrome
• Nivelon–Nivelon–Mabille syndrome
• NMDA receptor antagonist neurotoxicity (NAN)

• Nuchal bleb, familial
• Nut allergy
• Nyctophobia
• Nystagmus

• Nystagmus, central
• Nystagmus, peripheral
• Nystagmus with congenital zonular cataract