Letters to the editor

Abstract

A 60 year old woman presented in October 1982 with a 6-week history of progressive proximal muscle weakness in the upper and lower limbs. She had smoked 20 cigarettes per day for 40 years. On examination she was found to be emphysematous with generalized hyporeflexia and symmetrical proximal muscle weakness.Electromyographic (EMG) studies revealed normal motor nerve conduction velocities, sensory nerve action potentials, and distal latencies. The compound motor action potential (CMAP) in the right abductor pollicis brevis was 3 mV. Kepetitive stimulation at a rate of 2 Hz produced a 26% decrement in amplitude of the CMAP by the fourth response. Repetitive stimulation at 20 Hz provoked an incremental response of 400% with the CMAP amplitude increasing to 12 mV. Following a 2-minute period of isometric exercise, the CMAP was 4.5 mV, indicative of a degree of postexercise facilitation. The clinical and EMG features were diagnostic of LEMS, and an extensive search was undertaken for a systemic neoplasm without success. Hematological studies were normal. The white blood cell count (WBC) was 6.4 X 10"/L. Treatment was initiated with guanidine hydrochloride at a dose of 125 mg qid (10 mg/kg/day) and a successful response was obtained. The dose was, therefore, increased further to 250 mg qid (20 mg/kg/day), and muscle power returned to near normal.Five weeks after guanidine was commenced, a routine WBC was 3.5 X 10glL (neutrophils 2.27, lymphocytes 0.91). The dose of guanidine was, therefore, reduced to 150 mg qid (12 mg/kg/day).One week later her WBC was 2.8 X 10g/L (neutrophils 1.14, lymphocytes 1.23). Guanidine was ceased immediately, and 36 hours later a sternal bone marrow aspirate was performed, showing an adequate number of granulocytic precursors. N eutrophil antibody studies were negative.Four days after termination of guanidine therapy, the patient's WBC had risen to 6.6 x 1Oy/L (neutrophils 4.3), but she was significantly weaker. Guanidine was re-instituted at 125 mg qid under prednisone cover of 60 mglday. The WBC remained stable, and the prednisone was gradually phased out over 6 weeks.