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

Contents

• O–Ob
• Oc
• Occ–Och
• Ocu
• Od–Ok
• Ol
• Om–On
• Op
• Opi-Ops
• Opt
• Or
• Ora–Orn
• Oro–Ort
• Os
• Ose–Oss
• Ost
• Ot–Ox

O–Ob

• O Doherty syndrome
• O Donnell Pappas syndrome
• Obesophobia
• Obsessive–compulsive disorder (OCD)
• Obsessive–compulsive personality disorder
• Obstructive asymmetric septal hypertrophy
• Obstructive sleep apnea

Oc

Od–Ok

• Odonto onycho dysplasia with alopecia
• Odontoma
• Odontomicronychial dysplasia
• Odontoonychodermal dysplasia
• Odontophobia
• Odontotrichomelic hypohidrotic dysplasia
• OFD syndrome type 8
• OFD syndrome type Figuera
• Ogilvie's syndrome
• Ohaha syndrome
• Ohdo–Madokoro–Sonoda syndrome
• Oikophobia
• Okamuto–Satomura syndrome

Ol

• Olfactophobia
• Oligodactyly
• Oligodactyly tetramelia postaxial
• Oligomeganephronic renal hypoplasia
• Oligomeganephrony
• Oligophernia
• Oliver–McFarlane syndrome
• Oliver syndrome
• Olivopontocerebellar atrophy deafness
• Olivopontocerebellar atrophy type 1
• Olivopontocerebellar atrophy type 2
• Olivopontocerebellar atrophy type 3
• Olivopontocerebellar atrophy
• Ollier disease
• Olmsted syndrome
• Olney's lesions

Om–On

• Omenn syndrome
• Omodysplasia type 1
• Omodysplasia type 2
• Omphalocele cleft palate syndrome lethal
• Omphalocele exstrophy imperforate anus
• Omphalomesenteric cyst
• Omsk hemorrhagic fever
• Onat syndrome
• Onchocerciasis
• Oncocytoma
• Ondine's curse
• Oneirophobia
• Onychocryptosis
• Onychogryphosis
• Onycholysis
• Onychomadesis
• Onychomatricoma
• Onychomycosis
• Onychonychia hypoplastic distal phalanges
• Onychophosis
• Onychotrichodysplasia and neutropenia

Op

Or

Os

Ot–Ox

• Ota–Appaura syndrome
• Ota–Kawamura–Ito syndrome
• Oto-palato-digital syndrome type I and II
• Otodental syndrome
• Otofaciocervical syndrome
• Otoonychoperoneal syndrome
• Oto-Palatal-digital syndrome
• Otopalatodigital syndrome type 2
• Otosclerosis, familial
• Otosclerosis
• Otospondylomegaepiphyseal dysplasia
• Ouvrier–Billson syndrome
• Ovarian cancer
• Ovarian carcinosarcoma
• Ovarian dwarfism as part of Turner syndrome
• Ovarian dwarfism
• Ovarian insufficiency due to FSH resistance
• ovarian remnant syndrome
• Overfolded helix
• Overgrowth radial ray defect arthrogryposis
• Overgrowth syndrome type Fryer
• Overhydrated hereditary stomatocytosis
• Overwhelming post-splenectomy infection (OPSI)
• Oxalosis