We describe the case of a 13-year-old girl suffering from chondrodysplasia punctata, associated with ichthyosis arranged along Blaschko's lines, follicular atrophoderma, cicatricial alopecia and coarse, lusterless hair. The patient also showed a congenital cataract of the right eye, dysplastic facial appearance and symmetrical shortening of the tubular bones. The pathogenetic concept of functional X-chromosome mosaicism is reviewed as well as the recent results obtained by molecular research that have failed, so far, to solve the problem of regional assignment of the underlying X-linked gene.