In 1975, Neuhaüser (Z Kinderheilk 120:1-8) reported on a recessively inherited entity comprising mental retardation, megalocornea, and seizures. The megalocornea-mental retardation (MMR) syndrome (MIM 249310) is a rare entity. There have been 19 previously published cases and the clinical differences observed between reported patients have raised questions regarding the nosology of the syndrome and the issue of heterogeneity versus variability. We report on a new case: a 2 6/12-year-old boy, first child of nonconsanguineous healthy parents with megalocornea (corneal diameter > or = 13 mm), delayed psychomotor development and hypotonia, plus minor facial anomalies.