Obsessive Compulsive disorder
Obstetric Brachial Plexus Palsy see Erb's Palsy
Occlusive Infantile Arteriopathy see Metabolic diseases
Occupational Lung diseases see Lung diseases
OCD see Obsessive Compulsive disorder
Ocular Albinism see Albinism
Ocular Muscular Dystrophy see Muscular Dystrophy and neuromuscular disorders
Ocular Myasthenia see Myasthenia Gravis and other Myasthenic syndromes
Oculo-Cerebro-Renal syndrome see Lowe syndrome
Oculo-Cutaneous Albinism see Albinism
Oculoauriculovertebral Dysplasia see Goldenhar syndrome
Oculopharyngeal Muscular Dystrophy see Muscular Dystrophy and neuromuscular disorders
Oesophageal Atresia see Tracheo-Oesophageal Fistula and/or Oesophageal Atresia
Ohdo Blepharophimosis syndrome see Ohdo syndrome
Ohdo syndrome
Ohtahara syndrome
Oligoarthritis see Arthritis (Juvenile Idiopathic)
Olivopontocerebellar Atrophy see Metabolic diseases
Ollier disease
Omenn's syndrome see Primary Immunodeficiencies
Ondine's Curse see Congenital Central Hypoventilation syndrome
Ondine's see Congenital Central Hypoventilation syndrome
Opitz FG syndrome see Opitz-Kaveggia syndrome/FG syndrome
Opitz G/BBB syndrome
Opitz-Frias syndrome see Opitz G/BBB syndrome
Opitz-Kaveggia syndrome/FG syndrome
Oppositional Defiant disorder see Conduct disorder and Oppositional Defiant disorder
Opsoclonus-Myoclonus see Dancing Eye syndrome
Optic Nerve hypoplasia
Organic Acidaemias
Ornithinaemia see Metabolic diseases
Ornithine Transcarbamylase see Urea Cycle Disorders
Oromandibular Dystonia see Dystonia
Osgood Schlatter disease see Perthes disease
Osler-Rendu-Weber see Hereditary Haemorrhagic Telangiectasia
OSMED see Stickler syndrome
Osteoarthritis see Arthritis (Adult)
Osteochondritis of the Upper Femoral Epiphysis see Perthes disease
Osteodysplasia see Melnick-Needles syndrome
Osteodysplasty see Melnick-Needles syndrome
Osteogenesis Imperfecta see Brittle Bone diseases (Osteogenesis Imperfecta)
Osteopetrosis
Osteoporosis (Adult)
Osteoporosis (Juvenile)
Osteoporosis see Osteoporosis (Adult)
Osteoporosis see Osteoporosis (Juvenile)
OTC deficiency see Urea Cycle Disorders
Oto-Spondylo-Megaepiphyseal Dysplasia see Stickler syndrome
Oxygen Dependency see Broncho Pulmonary Dysplasia