Two Cases of X-Linked Myotubular Myopathy with Novel MTM1 Mutations.

BACKGROUND

Myotubular myopathy (MTM) is a congenital myopathy characterized by centrally placed nuclei in muscle fibers. Mutations in the myotubularin 1 gene (MTM1) have been identified in the most of the patients with the X-linked recessive form.

CASE REPORT

This report describes two male infants with X-linked MTM (XLMTM). Both patients presented with generalized hypotonia and respiratory difficulties since birth. We did not perform a muscle biopsy in either patient, but their conditions were diagnosed by genetic testing of MTM1. One splicing mutation, c.63+1G>C, and a frame-shift mutation, c.473delA (p. Lys158SerfxX28), were identified. Neither mutation has been reported previously.

CONCLUSIONS

Genetic testing for MTM1 is helpful for the differential diagnosis of floppy male infants. We suggest that advanced molecular genetic testing may permit a correct diagnosis while avoiding invasive procedures.