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.