Diagnosis of distal 22q11.2 deletion syndrome in a patient with a teratoid/rhabdoid tumour.

We report an 18 year old patient with mild intellectual disability who was diagnosed with a late onset teratoid/rhabdoid tumour by histological and immunohistochemical studies. Array-CGH studies, performed on a peripheral blood sample, showed a 3.4Mb deletion of chromosome 22q11.2, distal to the common DiGeorge syndrome (DGS) or Velocardiofacial syndrome (VCFs) region. This deletion is consistent with a diagnosis of distal 22q11.2 deletion syndrome. The deletion encompasses the INI1/SMARCB1 tumour suppressor gene. Biallelic inactivation of this gene is characteristic of atypical teratoid/rhabdoid tumours. Although several constitutional chromosome conditions are known to have increased susceptibility to various forms of cancer, very little is known regarding the magnitude of risk for malignancy associated with distal 22q11.2 deletion syndrome. In view of this finding we suggest that patients diagnosed with distal 22q11.2 deletion syndrome undergo careful prolonged monitoring for this type of tumour. This case demonstrates the need to carefully assess regions found to be deleted in individuals, referred for dysmorphia and/or developments delay, by array-CGH for the presence of genes known to be implicated in malignancy.