An extra small metacentric chromosome in a mentally retarded boy.

When aged 11 years, he was seen again (Fig. He had moderate microcephaly (circumference 50 5 cm. 10th percentile 52 cm.). The eyes were normally situated and orientated; there were no obvious epicanthic folds (Fig. The ears were normal, the nose was broad and straight, the mouth was small and triangular, and the palate rather high and arched. The hairline showed no abnormalities but there was some degree of webbing of the neck. The thorax was asymmetrical,