Three Japanese patients with 3p13 microdeletions involving FOXP1

FOXP1 is known as the gene responsible for neurodevelopmental delay associated with language impairment. Broad clinical findings also include feeding difficulty, muscular hypotonia, and distinctive features. These findings are common between patients with loss-of-function mutations in FOXP1 and 3p13 microdeletion involving FOXP1. Thus, “FOXP1-related intellectual disability syndrome” is now recommended. After obtaining informed consent, chromosomal microarray testing was performed for patients with unknown etiology. We identified three Japanese patients with 3p13 microdeletions involving FOXP1. One of the patients showed an additional 1q31.3q32.1 deletion as de novo, which was rather considered as a benign copy number variant. This is the first report of patients with 3p13 microdeletions from Japan. All patients showed growth delay, moderate to severe developmental delay, hearing loss, and distinctive facial features including prominent forehead and mid facial hypoplasia. In addition, “square shaped face” commonly observed in all three patients may be a characteristic finding undescribed previously. From the obtained findings, “FOXP1-related intellectual disability syndrome” was considered to be clinically recognizable.