Wolf‐Hirschhorn syndrome is a multiple congenital anomalies/mental retardation disorder due to deletion of the short arm of chromosome 4. A more complete delineation of the phenotype and better definition of this condition has only been possible in the last two decades. Until recently, it was commonly stated that development is severely compromised in affected individuals, and only recent large studies have allowed recognition of a much wider clinical spectrum.

Over recent years interest in the study of behavior phenotypes has gained increasing momentum. We present three white female patients, age respectively 9 years 9 months, 14 years 6 months and 18 years at the time of the last observation, seen because of developmental delay/mental retardation, seizures and learning disabilities. Cytogenetic analysis showed a de novo deletion of the short arm of chromosome 9 in all three, with the breakpoint being located at band 9p22. Although several studies have described the somatic phenotype, analytical evaluation of verbal and non-verbal cognitive functions are lacking. Our patients received a detailed neuropsychological and linguistic evaluation that showed a particular behavior profile, in the context of mental retardation of variable degree. On selective tests there was a marked deficit in visuo-praxic and visuo-spatial skills associated with memory disturbance. Visuo-motor integration abilities [VMI; Beery, 1997] and visuo-perceptual and visuo-spatial abilities [Benton line orientation test, 1992] seemed particularly impaired, both in relation to verbal mental age (vocabulary and grammatical production/comprehension) and to some non-verbal competencies [Benton face recognition test, 1992]. The profile shows advanced performances in face recognition. In addition, there is also a dissociation between verbal and visuo-spatial short term memory. This behavior phenotype is similar to that of Williams syndrome (WS) individuals. Our patients also showed some unusual within-domain dissociations regarding linguistic abilities. To better demonstrate similarities and differences between the behavior phenotypes of the del (9p22) syndrome and WS, we studied three IQ-gender-matched WS subjects. The comparison between the cognitive phenotypes of the two syndromes shows similarities in neuropsychological pattern. We hypothesize that there is a gene within the 9p22 region responsible for the neuropsychological profile described here.

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