Congenital idiopathic inability to perceive pain: a new syndrome of insensitivity to pain and itch with preserved small fibers.

Individuals vary widely in their sensitivity to painful stimuli. Some exhibit heightened reactions to pain (hyperpathia), while others show relative indifference. Although multiple factors may be responsible for these differences, varying sensitivities to pain also can be due to underlying differences in nociceptive neurophysiology. We present here the case of an individual with an apparent congenital inability to perceive pain. This patient appears to be different from other reported cases of insensitivity to pain described in the medical literature. He exhibited no evidence of an abnormality of the peripheral or autonomic nervous system and no apparent abnormality of the central nervous system other than isolated deficits in pain and temperature perception. Since pain is a subjective phenomenon, there is no definitive way to assess this patient's reported inability to perceive painful somatic stimulation, but available evidence suggests he has a defect in the supraspinal processing of nociceptive stimuli which renders him insensitive to pain. This raises the possibility of either deficient central nociceptive functioning or aberrant endogenous anti-nociceptive functioning.