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Unusual cognitive and behavioural profile in a Williams syndrome patient with atypical 7q11.23 deletion
  1. C Gagliardi1,
  2. M C Bonaglia1,
  3. A Selicorni2,
  4. R Borgatti1,
  5. R Giorda1
  1. 1IRCCS “E Medea”, Bosisio Parini, Lecco, Italy
  2. 2Clinica Pediatrica De Marchi, Milano, Italy
  1. Correspondence to:
 Dr R Giorda, IRCCS “E. Medea”, Via Don Luigi Monza 20, 23842 Bosisio Parini (LC), Italy; 
 rgiorda{at}bp.lnf.it

https://doi.org/10.1136/jmg.40.7.526

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    Williams syndrome (WS, MIM 194050) is a rare (frequency 1/20 000) multisystemic disorder1 caused by haploinsufficiency of genes at 7q11.23.2–4 WS is associated with dysmorphic facial features, supravalvular aortic stenosis (SVAS) and other cardiovascular diseases, infantile hypercalcaemia, and growth deficiency. The full intelligence quotient (IQ) of WS subjects is usually in the 50s to 60s, with a unique cognitive profile, characterised by relatively good verbal abilities alongside a low level of spatial and constructive organisation.5–7 This different pattern of abilities has been named the “WS cognitive profile” (WSCP).8

    More than 95% of clinically defined WS patients have a de novo deletion of about 1.5 Mb, with the breakpoints clustered within two highly homologous regions flanking the WS region.9 Several genes have been mapped within the deleted region,10 including syntaxin 1A (STX1A)11 that codes for a component of the synaptic apparatus, and RFC212 that encodes a subunit of the replication factor C complex.

    While ELN haploinsufficiency has been associated with the cardiovascular and possibly connective tissue abnormalities of WS,13 the role of other genes in the remaining clinical features of the disease is not known. In particular, it is not clear which gene(s) is responsible for the cognitive and personality profile characteristic of WS patients. It has been reported8 that patients with deletions of only ELN and LIMK1 show the characteristic WSCP, generally without mental retardation, but analysis of additional patients harbouring small deletions involving ELN and LIMK114 did not confirm these results. Limk1 deficient mice exhibit significant abnormalities in spine morphology and synaptic function. They also show altered spatial learning and fear response.15 The CYLN2 gene, coding for the cytoplasmic linker protein CLIP-115,16 localised in the dendritic lamellar bodies of neurones and cerebellar glia …

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