Obstructive hydrocephalus (also called non-communicating hydrocephalus) is a form of hydrocephalus which is caused by some visible blockage in the flow of cerebrospinal fluid.

Hyd...

Ochoa Syndrome is a rare inherited disorder characterized by inverted facial expressions.

Ocular Convergence Spasm is a rare disorder where the eyes turn towards each other.

Ocular Melanoma is a rare type of melanoma of the eye.

Oculocutaneous Albinism is a rare disorder characterized by a partial or total lack of melanin pigment in the eyes, skin and hair.

Oculodentodigital Syndrome is a rare genetic disorder resulting in small eyes, underdeveloped teeth, and malformation of the fourth and fifth fingers.

Oculofaciocardiodental Syndrome is a rare disorder causeed by the deletion of the BCOR gene affecting the eyes, face, teeth, and heart.

Ohdo Syndrome is a rare disorder characterized by learning disabilities associated with congenital heart disease, blepharophimosis (small eye openings), blepharoptosis (drooping eyelids), and small...

Olivopontocerebellar Atrophy (OPCA) is a term used to define neuronal degeneration in the cerebellum, pontine nuclei, and inferior olivary nucleus.

Ollier's Disease is a disorder when multiple sites in the body develop cartilage cyst found in the bone marrow.

Ondine syndrome is a rare respiratory disorder that is fatal if untreated.

Opitz G/BBB Syndrome is a genetic disorder caracterized by wide-spaced eyes; and breathing problems and difficulty swallowing.

Oral Lichen Planus is an inflammatory condition affecting the lining of the mouth. It occurs most often on the inside of the cheeks, but can affect the gums, tongue, lips and other parts of the mou...

Ornithine Transcarbamylase Deficiency is a rare metabolic disorder the affects the enzyme ornithine transcarbamylase and the body's ability to get rid of ammonia.

Orotic Aciduria Hereditary is a rare metabolic disorder characterized by the body's inability to break down orotic acid.

Osteochondritis Dissecans is a rare joint disorder in which cracks form in the articular cartilage and underlying subchondral bone.

Osteogenesis imperfecta (OI) is a group of rare genetic disorders that affect the bones and its connective tissues. Affected individuals have extremely brittle bones...

Osteoporosis pseudoglioma syndrome is a rare genetic disorder characterized by severe juvenile onset of osteoporosis and vision loss resulting from retinal detachment due to an inflammatory eye con...

Ouvrier-Billson Syndrome usually shows up in an infant before the age of 12 months and is characterized by eyes drifting up in an upward gaze and fluttering. The child compensates by lowering their...