Bone mineral density in familial amyloid polyneuropathy and in other neuromuscular disorders

Neuromuscular diseases are a known risk factor for immobilization-induced osteoporosis. The aim of the study was to analyse bone mineral density (BMD) in patients with familial amyloid polyneuropathy (FAP) type I (Val30 Met) and to compare them with a population of patients with other neuromuscular disorders. We studied 24, ambulatory, neuromuscular patients, all men and premenopausal women. We included 12 FAP patients (GI) and 12 patients with other disorders (GII). Clinical data included age, sex, height, weight, alcohol intake, smoking, calcium intake, physical activity and history of fractures. Serum and urinary calcium, osteocalcin, bone alkaline phosphatase, parathyroid hormone, thyroid stimulating hormone and urinary N-telopeptide cross-linked type 1 collagen were determined in all patients. Bone mineral density of lumbar spine, hip and wrist were determined by dual energy X-ray absorptiometry scan. No statistical differences were found in clinical or analytic data between the two groups, except for body mass index and calciuria, which were lower in GI. In GI, 54.5% were osteoporotic, against 23.1% in GII (P = 0.04). Bone mineral density was lower in GI when compared with GII, and tended to decrease with disease duration. Decreased BMI and the early autonomic involvement in GI probably explain the results. The prevention and early treatment of osteoporosis, in FAP patients should be considered a priority.