Jacobsen Syndrome is a rare disorder resulting from deletion of a part of chromosome 11 causing mild mental retardation, a distinctive facial appearance, and various physical problems.

Jarcho-Levin Syndrome is a rare hereditary skeletal growth disorder.

Jejunal Atresia is a rare genetic disorder caused by the partial absence of the fold of the stomach membrane that connects the small intestine to the back wall of the abdomen resulting in the jejun...

Johanson-Blizzard syndrome is a rare disorder characterized by abnormal development of the pancreas, nose and scalp, with mental retardation, hearing loss and growth failure.

Joubert Syndrome is a rare genetic disorder that affects the cerebellum, an area of the brain that controls balance and coordination.

Juvenile Rheumatoid Arthritis is a long-term (chronic) disease resulting in joint pain and swelling that affects children.

Juvenile X-Linked Retinoschisis is a rare genetic disorder primarily affecting young men.