We report a child with short stature, osteopenia with metaphyseal striations and severe mental retardation. This child shows radiological and clinical features of SPONASTRIME dysplasia. Only three sibships with this disorder have been reported. In two families, affected patients were of normal intelligence. In the third one, as well as our case, the dysplasia was complicated by severe mental retardation of unknown origin. The severity of the retardation in our case and a previous report, and some difference in the gestalt and radiological aspects, suggest that SPONASTRIME dysplasia is a heterogeneous disorder. We provisionally propose to split SPONASTRIME dysplasia in two phenotypically distinct subgroups, and to delineate here a 'new' variant with microcephaly and severe mental impairment.