A comparison of neuropsychological function between monozygotic twins with neurofibromatosis, type 1: A case report.

Objective: Neurofibromatosis type 1 (NF-1) is an autosomal dominant genetic disorder that commonly presents with cognitive impairment and greater rates of learning disorders and academic difficulty compared to the general population. Investigations of neurological and physiological expression of NF-1 in monozygotic twins identified intrapair similarities and differences. Monozygotic twins with NF-1 have been found to have similar IQ scores as well as concordant diagnoses of attention-deficit/hyperactivity disorder and learning disabilities. There have been no previous reports on similarities and differences in neuropsychological profiles between monozygotic twins with NF-1. The purpose of this article is to examine the results of comprehensive neuropsychological evaluations for a pair of monozygotic twins with NF-1. Method: A pair of 19-year-old female, African-American monozygotic twins with NF-1 underwent neuropsychological evaluations in an outpatient clinic. Findings are reported following the CAse REport (CARE) guidelines. Results: The twins demonstrated similar impairment in processing speed, working memory, and attention span; however, differences also were found. Conclusions: Intrapair similarities and differences on neuropsychological assessment were found between monozygotic twins with NF-1. Primary deficits were suggestive of a frontal-subcortical pattern and could be consistent with remote neuroimaging. When differences did occur, performance was typically better for Twin A, who had also showed greater improvement on neuroimaging. Implications and directions for future research are discussed. Specifically, this case demonstrates the need for inclusion of neuropsychological assessment in studies of larger cohorts of monozygotic twins with NF-1 and correlation of neuropsychological findings with neuroimaging and postzygotic mutations.