Inherited variation in Rieger's malformation.

RIEGER (1935) gave the accurate and self-explanatory name "dysgenesis mesodermalis corneae et iridis" to an inherited malformation involving the angle of the anterior chamber, iris stroma, and peripheral cornea. The basic feature of this abnormality was the presence of strands of iris stroma which passed from the iris root across the angle. to the trabecular meshwork and to a congenital corneal opacity at the end of Descemet's membrane, known as posterior embryotoxon. Other less suitable names given to the abnormality include congenital hyaline membrane on the posterior surface of the cornea (Mann, 1933), dysgenesis mesostromalis (Hagedoorn, 1937), posterior marginal dysplasia (Streiff, 1949), and Axenfeld's syndrome (Axenfeld, 1920). As these different terms suggest, there were various opinions on the developmental origin and characteristic features of the malformation. Embryological studies, notably those by Allen, Burian, and Braley (1955), suggested that Rieger's malformation was due to dysplasia of primitive angle mesoderm from which the trabecular meshwork and iris stroma are derived. Clinical and genetic features have been reviewed by Waardenburg, Franceschetti, and Klein (1961), who had difficulty in classifying reports of isolated and familial cases because of the great variability in clinical findings. In certain families the malformation was associated with dental and other ectodermal anomalies (Kittel, 1956; Gassler and Berthold, 1960). Where two or more generations could be studied, Rieger's malformation was apparently due to a dominant gene, but Waardenburg showed that there was not enough information to draw conclusions on the variability of gene effect among members of the same family. This problem has been examined further in the present investigation of a family living in the Oxford area.