The authors report the case of a female 5-months-old child who presented from the age of two months delayed neuromotor development, marked hypotonia, general muscle weakness and bilateral palpebral ptosis. The muscle biopsy revealed many fibers with central nuclei and the diagnosis was centronuclear (myotubular) myopathy. The difficult histological characterization of this congenital myopathy and the great variability of clinical findings with light, moderate or severe involvement are analysed and discussed.