Chromosome 15q BP3 to BP5 deletion is a likely locus for speech delay and language impairment: Report on a four-member family and an unrelated boy

Background: Deletions in chromosome 15q13 have been reported both in healthy people and individuals with a wide range of behavioral and neuropsychiatric disturbances. Six main breakpoint (BP) subregions (BP1-BP6) are mapped to the 15q13 region and three further embedded BP regions (BP3-BP5). The deletion at BP4-BP5 is the rearrangement most frequently observed compared to other known deletions in BP3-BP5 and BP3-BP4 regions. Deletions of each of these three regions have previously been implicated in a variable range of clinical phenotypes, including minor dysmorphism, developmental delay/intellectual disability, epilepsy, autism spectrum disorders, behavioral disturbances, and speech disorders. Of note, no overt clinical difference among each group of BP region deletions has been recorded so far. Methods: We report on a four-member family plus an additional unrelated boy affected by a BP3-BP5 deletion that presented with typical clinical signs including speech delay and language impairment. A review of the clinical features associated with the three main groups of BP regions (BP4-BP5, BP3-BP5, and BP3-BP4) deletions is reported. Results: Array-CGH analysis revealed in the mother (case 1) and in her three children (cases 2, 3, and 4), as well as in the unrelated boy (case 5), the following rearrangement: arr (hg19) 15q13.1-q13.3 (29.213.402–32.510.863) x1. Conclusion: This report, along with other recent observations, suggests the hypothesis that the BP region comprised between BP3 and BP5 in chromosome 15q13 is involved in several brain human dysfunctions, including impairment of the language development and, its deletion, may be directly or indirectly responsible for the speech delay and language deficit in the affected individuals.