3-M syndrome: a prenatal ultrasonographic diagnosis

The ultrasonographic imaging of a fetus affected by 3-M syndrome is described. This is a primordial dwarfism with low birthweight, short stature, facial dysmorphism and normal mental development. The biparietal diameter and head circumference were in accordance with the gestational age at 18 weeks. The femur and tibia lengths were on the fifth centile and the radius, ulna and humerus lengths were below the fifth centile. A second scan at 22 weeks showed slowing of growth of all long bones, with the femur, tibia, fibula, humerus, radius and ulna lengths further below the fifth centile. The pregnancy was terminated and postmortem examination confirmed the prenatal diagnosis. The differential diagnosis of skeletal dysplasias characterized by a slow growth of long bones is discussed and the conclusion reached that the detection of shortened long bones (below the fifth centile) is the only ultrasonographic finding of 3-M syndrome.