Familial centronuclear myopathy: a haploid DNA disease?

In the same family three boys (ages 8, 11, 14 years), suffering from a slowly progressive weakness of the flexors of the head and distal muscle groups of the extremities, were found to have a myopathy characterized by the presence of central nuclei in type I fibres. Their mother showed no histopathologic signs but a myopathic pattern on electromyography could be demonstrated. Cytophotometric examination of the anterior tibial muscle of these siblings revealed a reduction in DNA content by 50% in the central and subsarcolemmal nuclei (haploid DNA content) when compared with subsarcolemmal nuclei (diploid DNA content) of the same muscle of their mother. Nuclear DNA concentration in fibrocytes did not differ significantly between members of the family. Therefore, it is assumed that the nuclei of muscle fibres are selectively affected by the disease process which is indicated by a haploid DNA content.