Adult-Onset Acid Maltase Deficiency

• Electrophysiological studies were performed on aneurally cultured muscle cells from one patient with adult-onset acid maltase deficiency (AAMD) and from controls. The cells from the patient with AAMD had a higher mean resting membrane potential, a lower input resistance, and a higher incidence of action potentials at resting membrane potential than the control cells. Therefore, sarcolemma maturation was not adversely affected. The AAMD cells had membrane thresholds and action potential amplitudes similar to those of the control cells, and rarely produced repetitive action potentials. Therefore, the membrane instability noted in adult muscle fibers from the patient with AAMD was not present in cultured cells. This study does not support the suggestion that the biochemical and morphological abnormalities present in muscle fibers of patients with AAMD are sufficient to cause the electrical abnormalities.