Mutations in sodium-channel gene SCN9A cause a spectrum of human genetic pain disorders

Individuals with congenital indifference to pain have painless injuries beginning in infancy but otherwise normal sensory responses upon examination. Perception of passive movement, joint position, and vibration is normal, as are tactile thresholds and light touch perception. There is intact ability to distinguish between sharp and dull stimuli and to detect differences in temperature. The insensitivity to pain does not appear to be due to axonal degeneration, as the nerves appear to be normal upon gross examination (8). The complications of the disease follow the inability to feel pain, and most individuals will have injuries to lip or tongue caused by biting themselves in the first 4 years of life. Patients have frequent bruises and cuts, usually have a history of fractures that go unnoticed, and are often only diagnosed because of limping or lack of use of a limb. The literature contains very colorful descriptions of patients with congenital inability to perceive any form of pain.

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