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.