A 27-year-old Brazilian woman presented with a 7-month history of progressive pain, tingling, numbness, and weakness of the left upper limb, and paroxysmal dysesthesia affecting the left foot. On examination, there were erythematous, anesthetic patches of skin overlying the metacarpophalangeal joints and on the palmar surfaces of the hands (figure e-1 at Neurology.org/nn). There was congenital, bilateral campylodactyly and new flexion deformity of the fingers of the left hand with an incomplete range of passive extension. The intrinsic muscles of the left hand were wasted, particularly the thenar eminence and the dorsal interossei. Fasciculations were not observed. There was marked tenderness in the antecubital fossa and at the wrist, and the left superficial radial nerve was palpable. There was severe weakness of intrinsic finger movements, wrist flexion, and extension. Left upper limb reflexes were brisk and painful to percuss but tone, power, and reflexes including plantar responses were otherwise normal. Sensation to pinprick was reduced throughout the left hand with loss of temperature, vibration, and proprioceptive sensation distal to the wrist.