A new X-linked variant of spondylo-epimetaphyseal dysplasia with distinctive phenotype and severe mental retardation in three boys of one family is reported. The children were normal at birth. After several months of normal development progressive physical disability and slow mental deterioration were observed. Extensive biochemical tests were normal.
Conclusion: These patients represent a new form of X-linked spondylo-epimetaphyseal dysplasia.