[Myopathy in acromegaly. Report of two cases]

Acromegaly is often associated with neuromuscular disorders. Most of them are caused by compression of nerves with hypertrophic bone and soft tissues or complications of diabetes mellitus. Myopathy has rarely been reported in the Japanese literature. We report two cases with myopathy out of 14 cases of acromegaly. Case 1 is a 62-year-old woman who developed muscle weakness and atrophy in the shoulder girdle, pelvic girdle and femoral regions after a 10-year history of acromegaly. She showed positive Gowers' sign and normal DTRs. Basal growth hormone (GH) level in plasma was 1076 ng/ml. Electromyograms (EMG) obtained from the deltoid and rectus femoris muscles revealed typical myopathic abnormalities; an excess of small-amplitude, short-duration, polyphasic motor unit potentials. Histological examinations of the rectus femoris muscle showed diffuse atrophy of both type I and type II fibers. She also had bilateral carpal tunnel syndrome and bilateral tarsal tunnel syndrome, which were confirmed by nerve conduction studies of median nerves and posterior tibial nerves. A cranial computed tomography (CT) scan demonstrated sellar mass with suprasellar extension. She underwent transsphenoidal adenomectomy and radiation therapy. GH level lowered to 29 ng/ml, however, myopathy remained unchanged for 3 years after the surgery. Case 2 is a 38-year-old woman who had undergone partial removal of a pituitary adenoma 9 years after the onset of acromegaly. Basal GH level in plasma before the surgery had been 1694 ng/ml and was still high after the surgery (100-505 ng/ml). The patient developed proximal muscle weakness and atrophy 4 years after the surgery.(ABSTRACT TRUNCATED AT 250 WORDS)