[Unilateral presentation of X-linked myotubular myopathy (XLMTM) in two out of three female carriers in a family with no affected male].

INTRODUCTION

X-linked myotubular myopathy (XLMTM), a recessive disorder, is caused by mutations affecting the myotubulatin (MTM1) gene located on the X chromosome. Most of the affected males die in the early postnatal period whereas female carriers are usually asymptomatic.

CASE REPORTS: We report a family in which two females (45 and 27 years old) in two different generations, presented unilateral weakness which had worsened since adolescence, and one 48-year-old woman presented minimal symptoms. In agreement with the computed tomography and magnetic resonance imaging findings, the EMG was compatible with myopathy. Serum creatine kinase was elevated in the second patient. The histological study showed centronuclear myopathy aspects, more severe in the second patient. Both presented c.1420C>T, p.Arg474X in exon 13 of the MTM1 gene, whereas the third patients with less pronounced manifestation, had a skewed pattern of X chromosome inactivation.

DISCUSSION: Symptomatic female carriers of XLMTM can present with asymmetric malformations, which must be distinguished from an autosomal-dominant centronuclear myopathy.

CONCLUSION

Unilateral presentation of weakness cannot rule out a diagnosis of myopathy. Detection of symptomatic female carriers of an X linked recessive disease, with a severe presentation in males, is important for genetic counselling.