The X-linked Myotubular myopathy (XLMTM) due to mutations in the MTM1-gene (myotubularin 1) has been clinically well characterised and usually gives rise to a severe phenotype in males presenting at birth with severe congenital myopathy. Although the muscle morphological characteristics are currently well documented (significant number of small muscle fibres with centralised nuclei), the formation and maintenance of this particular structure is not well characterised in human. We aimed to correlate the pathologic features of skeletal muscle biopsy of newborns with MTM1-mutations according to the corrected gestational age, and to compare these morphological findings with the pathological characteristics of muscle in myotubularin1-deficient mice.