Leroy I-cell disease is a rare autosomal recessive lysosomal storage disorder characterized by marked psychomotor and growth retardation, skeletal anomalies, and typical facial features. There is a biochemical defect in uridine diphospho-N-acetylglucosamine-1-phosphotransferase, which is the enzyme responsible for addition of a mannose phosphate residue for lysosomal trafficking. Prenatal diagnosis is possible by analysis of enzyme activity in chorionic villi or cultured amniocytes, but this is offered to families only known to be at increased risk. We describe two cases that had bilateral shortness of the femurs at 25 and 31 weeks of gestation in the ultrasound scan and were diagnosed as Leroy I-cell disease by plasma enzyme analysis in the postnatal period. There was also bowing of the femurs in one case. None of the two families had a history of Leroy I-cell disease. The parents of one case were second-degree cousins. In view of these two cases that are presented, we propose that Leroy I-cell disease should be included in the differential diagnosis of short femurs even when there is no evident family history. Copyright (c) 2007 S. Karger AG, Basel.