Hamdan et al. (2010) reported 2 unrelated children of French Canadian origin with a developmental disorder characterized by mild to moderate mental retardation, language impairment, and autistic features. Both showed global delay, delayed walking, and severely delayed speech ... Hamdan et al. (2010) reported 2 unrelated children of French Canadian origin with a developmental disorder characterized by mild to moderate mental retardation, language impairment, and autistic features. Both showed global delay, delayed walking, and severely delayed speech development, with first words being spoken at age 3 and 6 years, respectively. Neither had evidence of an oromotor coordination defect. The first patient showed autistic features but did not meet full criteria due to some residual communication abilities, whereas the second patient met full criteria for autism (209850). Both patients showed severely limited expressive language, using single words or short sentences, although vocabulary was adequate in 1. Both showed better ability in receptive language comprehension. Both patients also showed behavioral abnormalities, including irritability, hyperactivity, aggression, and stereotypical rigid behaviors.
Hamdan et al. (2010) identified 2 different de novo heterozygous mutations in the FOXP1 gene (605515.0001 and 605515.0002, respectively) in 2 unrelated children of French Canadian origin with moderate mental retardation, expressive language deficits, and autism spectrum disorder ... Hamdan et al. (2010) identified 2 different de novo heterozygous mutations in the FOXP1 gene (605515.0001 and 605515.0002, respectively) in 2 unrelated children of French Canadian origin with moderate mental retardation, expressive language deficits, and autism spectrum disorder (ASD). The first mutation (605515.0001) was a small deletion found using array-based comparative genomic hybridization of a cohort of 80 patients with ASD and 30 with intellectual disability. The second mutation (R525X; 605515.0002) was found by direct sequencing of the FOXP1 gene in a cohort of 110 patients with intellectual disability, 84 with ASD, and 51 with both. Hamdan et al. (2010) chose to examine the FOXP1 gene specifically because of the role of the FOXP2 gene (605317) in a speech and language disorder (SPCH1; 602081); patients with intellectual disability and ASD often show language impairment. The results indicated that disruption of FOXP1 has a global impact on brain development.