Myopathy and primary aldosteronism: electronmicroscopic study.

We studied two patients with myopathy and primary aldosteronism. Necrosis and vacuolation of muscle fibers were found on light microscopy. Ultrastructurally, the necrotic areas were characterized by dissolution of myofilaments with degenerative vacuoles. In muscle fibers that did not show necrosis, there were membrane-bound vacuoles, dilation of the sarcoplasmic reticulum, widening of the T-system, and a "honeycomb" appearance of T-tubules. These ultrastructural features suggest that the necrosis of muscle fibers may originate from membrane vulnerability of the sarcoplasmic reticulum and the T-system.