New HSN2 mutation in Japanese patient with hereditary sensory and autonomic neuropathy type 2

Hereditary sensory and autonomic neuropathies (HSANs) are heterogenous disorders characterized by a loss of pain sensation and autonomic abnormalities caused by peripheral nerve degeneration. (1) HSANs are clinically classified into five entities based on the inheritance pattern and clinical presentations. Mutations in at least six genes, SPTLC1, RAB7, HSN2, IKBKAP, TRKA, and NGFB, are known to be causative for the clinical varieties of HSANs. (1) HSAN2 is clinically characterized by autosomal recessive inheritance, the onset of symptoms in infancy or early childhood, the occurrence of paronychia, whitlows, ulcers of distal extremities, unrecognized fractures of the foot and hand, anhidrosis, sensory loss that affects all modalities of sensations in the lower and upper limbs, the absence or diminution of tendon reflexes, the absence of sensory nerve action potentials (SNAPs), and the virtual absence of myelinated fibers with a decreased number of unmyelinated fibers in sural nerves. (1) To date, seven truncated mutations of the HSN2 gene have been identified among HSAN2 families from Quebec, Newfoundland, and Nova Scotia in Canada, and Lebanon, Italy, and Austria. (2-5) Here, we describe a new truncated mutation in the HSN2 gene of a Japanese patient with HSAN2.