Congenital universal insensitivity or indifference to pain has been reported in about 45 cases since Dearborn's1 first description of a man with unusual tolerance for pain. The emphasis of the reports has varied, and there has been great variation in the completeness of recording of historical, neurological, and biopsy data. As recently as 1961, Kunkle2 pointed out that the available information still makes it difficult to determine whether many of the recorded cases are lacking in the ability to perceive pain "insensitivity" or have an abnormal lack of the appreciation of pain "indifference."
Biopsy of peripheral nerves has permitted identification of some cases of peripheral neuropathy,3 but in other cases no such abnormalities have been found.3,4,5 Only two detailed neuropathologic studies have been reported in cases coming to autopsy6,7; neither revealed significant abnormalities, so that one is justified in classifying these as cases of congenital
SWANSON AG, BUCHAN GC, ALVORD EC. Anatomic Changes in Congenital Insensitivity to PainAbsence of Small Primary Sensory Neurons in Ganglia, Roots, and Lissauer's Tract. Arch Neurol. 1965;12(1):12–18. doi:10.1001/archneur.1965.00460250016002