Increased morphological variants in children with learning disabilities.

Previous studies have shown that children with learning disabilities have more morphological variants or anomalies than normal children, suggesting that the morphological and central nervous system effects may be the result of the same prenatal factors. The morphological variants were assumed to have arisen in the first 3 months of prenatal development, which may not be so. We have partitioned variants into those that probably arise early in fetal development ("early" variants) and those that could arise later and could be due to altered growth ("late" variants). There was an increase in both "early" and "late" variants but only that the "late" variants was statistically significant. Although the method of measuring one "early" variant (dermal patterns) was sensitive enough to detect mild disturbances in children with isolated congenital heart disease, such a disturbance was not found in our group of learning-disabled patients. Our findings suggest that the developmental disturbances resulting in morphological variants may act later in prenatal development than was previously believed. This information may be helpful in searching for clues to the etiology of this heterogeneous group of disabilities.