Co-occurrence of achondroplasia and Down syndrome: Genotype/phenotype association.

BACKGROUND

This report describes the sixth case of an unusual association: Down syndrome with achondroplasia. It also analyzes the effects of both of these disorders on patient phenotype.

METHODS

A male infant was evaluated for Down syndrome. His appearance also suggested a diagnosis of achondroplasia. The child was evaluated by physical examination, radiography, cytogenetic study, and mutation analysis.

RESULTS

Chromosome analysis showed a karyotype of 47,XY,+21 in all 30 cells analyzed. Radiographic examination showed typical findings of achondroplasia, such as disproportionately large skull, shortening of limb segments, and lumbar lordosis. FGFR3 screening showed a heterozygous G1138A mutation.

CONCLUSIONS

The interaction of these two distinct genetic disorders in the same patient produces a phenotype typical of each syndrome with some overlapping signs. This case represents de novo origin of two disorders that both may be parental-age related.