Patient with double heterozygosity for achondroplasia and pseudoachondroplasia, with comments on these conditions and the relationship between pseudoachondroplasia and multiple epiphyseal dysplasia, Fairbank type.

We present a 7 1/2-year-old girl with achondroplasia and pseudoachondroplasia. Her mother has achondroplasia and her father has pseudoachondroplasia. Radiographic manifestations of these two conditions from infancy to age 6 years are outlined. The findings in this patient are compared with those of achondroplastic patients and pseudoachondroplastic patients of similar ages. Our review of radiographs of many pseudoachondroplastic patients and subsequently of those of patients with multiple epiphyseal dysplasia (MED), Fairbank type, reinforced our opinion that pseudoachondroplasia and multiple epiphyseal dysplasia, Fairbank type, are closely related conditions. MED, Fairbank type, may be the mildest form of pseudoachondroplasia. Recently published electron microscopic findings also suggest this.