What is (are) Hereditary sensory and autonomic neuropathy ?
Hereditary sensory autonomic neuropathy (HSAN) is a group of rare peripheral neuropathies where neurons and/or axons are affected. The major feature of these conditions is the loss of large myelinated and unmyelinated fibers. Myelin is an insulating layer, or sheath that forms around nerves, made up of protein and fatty substances, that allows electrical impulses to transmit along the nerve cells. If myelin is damaged, these impulses slow down. Symptoms of HSAN include diminished sensation of pain and its associated consequences of delayed healing, Charcot arthopathies, infections, osteomyelitis, and amputations. They have been categorized into types one through five, although some children do not fit well into this classification and do not all have altered pain sensation and/or autonomic function.[9873] HSAN type I is the most common form of HSAN. It is caused by a mutation in the SPTLC1 gene and inherited in an autosomal dominant pattern. HSAN type 2 is caused by mutations in the WNK1 gene and inheritance is autosomal recessive . HSAN type 3 (Riley-Day syndrome or familial dysautonomia) is caused by mutations in the IKBKAP gene and inheritance is autosomal recessive. HSAN type 4, also called congenital insensitivity to pain with anhidrosis (CIPA), is caused by mutations in the NTRK1 gene and is an autosomal recessive disorder. HSAN type 5 is caused by mutations in the NGFB gene and inherited in an autosomal recessive manner.