Evidence for a discrete behavioral phenotype in the oculocerebrorenal syndrome of Lowe

The oculocerebrorenal syndrome of Lowe (OCRL) is an X-linked disorder characterized by congenital cataracts, cognitive impairment, and renal tubular dysfunction. Although there is a wide range of intellectual function in affected individuals, it is often compromised by a high prevalence of maladaptive behaviors, including tantrums, stubborness, and stereotypy. Whether these behaviors simply reflect the multiple disabilities found in some developmentally impaired individuals with or without OCRL, or a specific genetically-determined behavioral phenotype of OCRL, is unknown. Controls were matched for sex, age, visual impairment, and adaptive functioning and compared with OCRL patients on three standardized measures of adaptive/maladaptive behaviors. Forty-three matched pairs of OCRL and control subjects were identified. Both groups were similar in communication, daily living, socialization, and motor skills, in socioeconomic status, and in measures of parental stress. Individuals with OCRL displayed significantly more severe maladaptive behaviors than control boys, as measured by the Vineland Adaptive Behavior Scales (VABS), with 41% of the difference between the two groups attributable to the diagnosis of OCRL. Twelve maladaptive behaviors measured on the VABS appeared more frequently in OCRL than in controls. Five of these 12 behaviors, i.e., temper tantrums, irritability, complex repetitive behaviors (stereotypy)/mannerisms, obsessions/unusual preoccupations, and negativism, were identified by discriminant function analysis to significantly distinguish between controls and OCRL individuals. The diagnosis of OCRL is associated with a behavioral phenotype consisting of temper tantrums, stereotypy, stubborness, and obsessions/unusual preoccupations. This phenotype cannot be attributed solely to the visual, motor, and intellectual disabilities characteristic of OCRL, and may represent a specific effect of the OCRL gene on the central nervous system.