Hereditary sensory and autonomic neuropathy type II

Hereditary sensory and autonomic neuropathy type II (HSAN2) is a condition that primarily affects the sensory nerve cells (sensory neurons), which transmit information about sensations such as pain, temperature, and touch to the brain. These sensations are impaired in people with HSAN2. In some affected people, the condition may also cause mild abnormalities of the autonomic neurons, which control involuntary body functions such as heart rate, digestion, and breathing. The sensory and autonomic neurons are part of the body's peripheral nervous system, which comprises the nerves outside the brain and spinal cord. HSAN2 is considered a form of peripheral neuropathy.

The signs and symptoms of HSAN2 typically begin in infancy or early childhood. The first sign of the condition is usually numbness in the hands and feet. Soon after, affected individuals lose the ability to feel pain or sense hot and cold. In people with HSAN2, unnoticed injuries often lead to open sores (ulcers) on the hands and feet. Because affected individuals cannot feel the pain of these sores, they may not seek treatment right away. Without treatment, the ulcers can become infected and may require amputation of the affected area. People with HSAN2 often injure themselves unintentionally, typically by biting the tongue, lips, or fingers. These injuries may lead to loss of the affected areas, such as the tip of the tongue. Affected individuals often have injuries and fractures in their hands, feet, limbs, and joints that go untreated because of the inability to feel pain. Repeated injury can lead to a condition called Charcot joints, in which the bones and tissue surrounding joints are damaged.

The effects of HSAN2 on the autonomic nervous system are more variable. Some infants with HSAN2 have digestive problems such as the backflow of stomach acids into the esophagus (gastroesophageal reflux) or slow eye-blink or gag reflexes. Affected individuals may also have weak deep-tendon reflexes, such as the reflex being tested when a doctor taps the knee with a hammer.

Some people with HSAN2 lose a type of taste bud on the tip of the tongue called lingual fungiform papillae and have a diminished sense of taste.