Some devastating rare genetic diseases are Tay Sachs disease and Machado-Joseph disease, according to the National Organization for Rare Disorders. Bardet Biedl syndrome is a third, states the National Institutes of Health
In Tay Sachs disease, the body does not produce enough of an enzyme called hexosaminidase A, says the National Organization for Rare Disorders. This leads to a buildup of fats in the central nervous system. Because of this buildup of fats, babies who have Tay Sachs disease regress physically and mentally. Tay Sachs disease can also affect adults, though the progression of the disease is slower and may not be as devastating as that affecting young children.
Machado-Joseph disease is an inherited disease that attacks the central nervous system, asserts the National Organization for Rare Disorders. There are three types of this disease. Patient suffer weakness in their arms and legs, rigid muscles, and a clumsy gait that others may mistake for inebriation. They suffer bulging eyes, damaged eye muscles and problems with speaking and swallowing. In Type III Machado-Joseph disease, the patient loses sensation or experiences abnormal sensations and does not feel pain.
In Bardet Biedl syndrome, the patient suffers progressive loss of vision, extra toes and fingers, hypogonadism, learning difficulties, abnormalities in the kidneys and an unusual accumulation of fat around the chest and the torso, states the National Institutes of Health.