Congenital absence of pain.

A 16-year-old boy had congenital absence of pain sensitivity and no impairment of other sensory modalities. Routine electrophysiologic investigation showed no abnormalities. The threshold and latency of electrically elicited corneal reflex and cortical potentials evoked by tooth pulp stimulation were normal, but suprathreshold electric stimulation of corneal mucosa and dental pulp, as well as electric stimulation of dorsal roots, did not elicit pain. The total CSF opioid activity was raised. However, naloxone hydrochloride administration failed to reverse the analgesia. The axon reflex to intradermal injection of histamine dihydrochloride was absent. Cutaneous nerve branches showed unspecific changes affecting part of unmyelinated axons. most of the unmyelinated as well as the myelinated axons were normal. We consider the case an example of congenital indifference to pain.