Tubular aggregates. Their association with neuromuscular diseases, including the syndrome of myalgias/cramps.

Tubular aggregates of muscle are distinctive structures seen in a wide variety of disorders. We reviewed 1,500 consecutive muscle biopsy specimens for the presence of tubular aggregates. Fifteen biopsy specimens (1.0%) were found with this abnormality. All patients were male, and seven had specific diagnoses based on clinical, biochemical, morphologic, and electrophysiologic criteria: hypokalemic periodic paralysis (two patients); hyperkalemic periodic paralysis (one patient); myotonia congenita (one patient); inflammatory myopathies (three patients). The remaining eight patients had a syndrome characterized predominantly by muscle pain and/or cramps, not necessarily precipitated by exercise. Although tubular aggregates constituted the predominant abnormality on muscle biopsy specimens in these cases, other mild, nonspecific changes were noted.