Interstitial 2.2 Mb deletion at 9q34 in a patient with mental retardation but without classical features of the 9q subtelomeric deletion syndrome.

In a female patient with mild mental retardation an interstitial subtelomeric 9q34.3 deletion was identified by a multiplex ligation-dependent probe amplification (MLPA) based screen for subtelomeric abnormalities. Further characterization of the deletion by high-resolution tiling path array-based comparative genomic hybridization (array CGH) revealed a size of 2.2 Mb. The woman lacked the typical 9qter deletion phenotype characteristics, which is inline with the finding that both Eu-HMTase1 (EHMT) genes were present. However, she presented with mild mental retardation, some mild facial dysmorphisms and aplasia cutis. This is another example of an interstitial subtelomeric deletion, which underscores that further characterizing the precise nature of the deletion is of clinical importance. Moreover, it confirms the importance of the Eu-HMTase1 gene as the major causative factor of the classical 9qter syndrome phenotype.