BTG3 and Intellectual disability: The findings that patients 4 and 5 presented more severe clinical features than patients 1–3 are in agreement with previously reported cases (Table 1 and Fig. 2) [1, 2, 20], where the proximal 21q deletions encompassed two genes expressed in the central nervous system, RBM11 (21q11.2) and BTG3 (21q21.1), that might play a role in intellectual disability.