Neurobehavioral consequences of a genetic metabolic disorder: visual processing deficits in infantile nephropathic cystinosis.

The purpose of the current study was to further characterize the nature of the visual processing deficit in infantile nephropathic cystinosis. It was hypothesized that children with cystinosis would demonstrate a dissociation between visuospatial and visuoperceptual abilities, with impaired spatial functioning and intact perceptual functioning. Hypotheses were based on cognitive studies to date as well as on a review of the visual processing literature.Infantile nephropathic cystinosis is a genetic metabolic disorder in which the amino acid cystine accumulates in various organs, including the kidney, cornea, thyroid, and brain. The existing neurocognitive literature suggests the presence of a visual processing deficit against a background of generally normal intellectual capacity. The nature of the deficit, however, is still somewhat ambiguous.Study participants were 141 children (33 with cystinosis and 108 controls), ages 5 through 14 years. Tests of visuospatial and visuoperceptual functioning were administered.Data were analyzed using hierarchical regression analyses and MANCOVA. After covarying for relevant demographic variables, the cystinosis group consistently demonstrated impairments in spatial processing, whereas perceptual processing was largely intact.Results support the hypothesis of a dissociation in visual processing. Findings suggest that cystinosis has a differential effect on the two cortical visual processing streams, with spatial functions affected to a greater extent than perceptual functions. The present study has implications for brain-behavior relationships in other genetic disorders as well.