TWO English ophthalmologists, Laurence and Moon in 1886, directed attention to the fact that retinitis pigmentosa sometimes appears in combination with other defects, such as mental retardation, hypogenitalism, and obesity. In 1922, Biedl reported the additional observation of familial occurrence and polydactyly in association with the above findings. Thus, this complex became known as the Laurence-Moon-Biedl syndrome.1By definition, it is characterized by familial occurrence, 48%; mental retardation, 80%; obesity, 83%; genital dystrophy, 60%; retinitis pigmentosa, 68%; and polydactyly or syndactyly, 75%.2-4Numerous other anomalies such as skull defects, renal disease, and heart disease are often included but are not considered essential to the diagnosis.5-7The syndrome is seen in all races and occurs in children with healthy parents, although consanguinity of parents has been reported.8,9 Two theories of the genetic aspect of this syndrome have been proposed. One theory is that a single gene produces