Pseudoachondroplasia

Abstract

In 1959, Maroteaux and Lamy described a type of dwarfism which they called pseudoachondroplastic spondyloepiphyseal dysplasia. They pointed out that it was a condition which, radiographically and clinically, could be distinguished from classic achondroplasia. Individuals with pseudoachondroplasia are almost never recognized at birth. The onset of clinical symptoms and growth retardation usually does not occur until after one year of age. The average adult height, however, is less than in classic achondroplasia. These patients clinically resemble those with achondroplasia, having long trunks, increased lumbar lordosis and short limbs; hence, the name pseudoachondroplasia. However, in contrast to true achondroplastic dwarfs, these patients have normal craniofacial proportions. Roentgenographically, vertebral and epiphyseal changes evolve with time and are quite different from those in classic achondroplasia. Intelligence and life span are normal. Pseudoachondroplasia is a type of dwarfism which can be distinguished on clinical and roentgenologic grounds from other chondrodystrophies. Heterogeneity clearly exists within this group of patients. At least 2 types of recessively inherited pseudoachondroplastic patients can be distinguished from the dominantly inherited varieties. Probably heterogeneity exists among the dominant families, but this distinction is less clear. The authors think there are at least 2 dominantly inherited forms. The structural studies support the idea of heterogeneity. However, as yet no clear distinguishing features have been found, but rather only gradations in ultrastructural change. We do not feel that a sporadic individual case can be classified with confidence at this time; however, it seems likely that the recessive varieties can be distinguished from dominant cases on clinical and roentgenographic bases, allowing genetic counseling with regard to mode of inheritance.