Charcot neuro-osteoarthropathy (CNO), or Charcot foot, is a disabling complication of diabetes, which is poorly understood and frequently overlooked. We describe an atypical presentation of an active Charcot foot in a woman with a long-standing type 1 diabetes who did not exhibit loss of protective sensation (sensate to a 10-gram monofilament) or loss of vibration sensation. These standard measures of large nerve fibre function ruled out "classical" neuropathy. However, additional testing showed reduced sweat gland function most likely related to degeneration of c-fibres (small fibre neuropathy). This case raises the awareness that in addition to the "textbook" description, in diabetes, Charcot foot can develop in individuals with "minimal" or "no signs" of clinical neuropathy. The onset of active Charcot foot should be suspected in every person with diabetes and history of trauma even when foot and ankle x-rays are normal. Offloading should be initiated until the diagnosis is proven otherwise.
Keywords: Charcot foot; Charcot neuro-osteoarthropathy; diabetes; monofilament; peripheral neuropathy; vibration perception threshold.