Hereditary sensory and autonomic neuropathy type 2

Hereditary sensory and autonomic neuropathy type 2 (HSAN2), also known as congenital sensory neuropathy or hereditary sensory neuropathy type II, is a rare genetic disorder that primarily affects the peripheral sensory nerves. It is characterized by a severe reduction or complete loss of sensation to pain, temperature, and touch, predominantly in the distal extremities (hands and feet), though the sensory loss can be more widespread. The condition results from progressive degeneration of peripheral sensory neurons, particularly affecting myelinated and unmyelinated nerve fibers. Symptoms typically begin in infancy or early childhood. Because affected individuals cannot feel pain, they are highly susceptible to unnoticed injuries, burns, and fractures. Chronic skin ulcers, particularly on the feet, are common and can lead to secondary infections and, in severe cases, osteomyelitis requiring amputation of fingers or toes (acromutilation). Autonomic involvement is generally mild but may include reduced sweating and occasional episodes of low blood pressure. Nerve conduction studies typically show absent or severely reduced sensory nerve action potentials. Neuropathological examination reveals a marked loss of myelinated fibers in peripheral nerves. HSAN2 is caused by mutations in several genes, including WNK1/HSN2, FAM134B (RETREG1), KIF1A, and SCN9A, with autosomal recessive inheritance being the most common pattern. There is currently no cure or disease-modifying treatment for HSAN2. Management is supportive and focuses on prevention of injuries, meticulous wound care, regular monitoring for infections, protective footwear, and patient and family education about avoiding trauma. Orthopedic interventions may be necessary for fractures or joint complications such as neuropathic (Charcot) arthropathy.

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