Familial dysautonomia (Riley-Day syndrome).

Familial dysautonomia, also known as Riley-Day syndrome, is a disorder of autonomic nervous system with an autosomal recessive mode of inheritance. Reduction and/or loss of unmyelinated and small myelinated fibers is found, as reduction of dopamine beta-hydroxylase in blood. The diagnosis is based on clinical features: diminished lacrimation, insensitivity to pain, poor temperature control, abolished deep tendon reflexes, postural hypotension, vomiting attacks, poor motor coordination, and mental retardation.