Isolated myopathy as the initial manifestation of primary systemic amyloidosis.

Sirs: Primary systemic amyloidosis (AL) is an uncommon disorder in which immunoglobulin light chains are deposited in the tissues as amyloid, resulting in organ dysfunction [1]. Common presentations are nephrotic syndrome, cardiomyopathy, peripheral neuropathy or hepatomegaly [1, 4]. In contrast, amyloid myopathy (AM) is an unusual manifestation of AL [1, 9] and muscle weakness as the initial symptom of the disease is rare [1, 7, 11, 12] A 65-year old man, with no medical or family history, presented with 1-year muscle weakness, fatigue and 4.5kg weight loss. The weakness progressed so that he was unable to walk without support or lift his arms above his head. General physical examination was unremarkable. According to the Medical Research Council (MRC) scale, he had grade 3 in the neck flexors, extensors and the proximal upper extremities muscles bilaterally. Grade 4 was noted in the distal hand muscle groups. In the legs, the hip extensors, flexors and abductors were grade 2, the knee extensors and flexors grade 3 and ankle dorsiflexors and evertors were 4. There were no fasciculations, muscle atrophy, pseudohypertrophy, nodular lesions or macroglossia. All cranial nerves and the rest of the neurological examination were normal. An extensive hematological, biochemical and immunological investigation, including serum protein electrophoresis and immunoelectrophoresis, was either normal or negative. Erythrocyte sedimentation rate ranged from 59 to 66 mm/h. Echocardiography revealed concentric myocardial thickening, with an interventricular septal thickness of 1.6 cm (normal 0.6–1.1 cm), diastolic dysfunction, but normal valves, systolic ejection fraction and no “scintillating” appearance. Cervical spine MRI was normal. Neurophysiology revealed normal sensory and motor conduction velocities, amplitudes and distal latencies, with no significant decrement after stimulation at 3Hz. Needle EMG demonstrated positive waves and fibrillation potentials in all muscles tested. Early motor unit potentials (MUPs) were of short duration, low amplitude and polyphasic in all muscles examined. Maximal effort showed the same pattern of MUPs described above, except for the biceps and the first dorsal interosseous, in which short, high amplitude, polyphasic potentials were recorded. Recruitment was full and early in all muscles tested. A left deltoid muscle biopsy with frozen sections processed for hematoxylin-eosin demonstrated several angular atrophic and degenerated or necrotic muscle fibers, with no inflammatory cellular infiltration (Fig. 1). Congo red staining revealed amyloid deposits infiltrating the thickened walls of small intramuscular vessels (Fig. 2). No amyloid was observed surrounding or infiltrating muscle fibers. Immunoperoxidase showed lambda light chains in the affected vessel walls. His weakness deteriorated and 8 months later, he was confined to a wheelchair and had multiple nodular subcutaneous lesions. Biopsy from the skin and small intestine revealed diffuse amyloid deposition surrounding blood vessels in Congo red stained sections. Immunohistology for amyloid A and prealbumin was negative in both, establishing AL. During the next 4 months, colchicine treatment was ineffective and the patient died at home from cardiac arrest, at the age of 66 years. Lubarsch [5] first reported amyloid involvement of muscle with vascular and interstitial deposits in skeletal muscle and the LETTER TO THE EDITORS