Here we report a new case in which the clinical manifestation were compatible with the phenotype described by Lujan et al. [Am J Med Genet 1984; 17: 311-22] as 'X-linked mental retardation with marfanoid habitus'. Based upon the presence of mild psychomotor retardation, epilepsy and skeletal malformations, a sister can be considered an affected carrier, whereas an older brother showed skeletal abnormalities and juvenile glaucoma. The mother had bilateral palpebral ptosis with minimal mitochondrial abnormalities at muscle biopsy.