Background: Forkhead box protein 1 (FOXP1) (OMIM: 605515) at chromosomal region 3p14.1 plays an important regulatory role in cell development and functions by regulating genetic expression. Earlier studies have suggested that FOXP1, an oncogene, is capable of initiating tumorigenicity depending on the cell type. FOXP1 also plays an important role in regulating the cell development and functions of the immune system, e.g., regulating B-cell maturation and mononuclear phagocyte differentiation, and in the occurrence and development of various immune diseases. The mRNA of this gene is widely expressed in humans, and its differential expression is related to numerous diseases.
Case summary: A 5-year-old boy mainly presented with attention deficit and hyperactivity disorder and developmental retardation accompanied by gait instability and abnormal facial features (low-set ears). DNA samples were extracted from the child's and his parents' peripheral blood to detect whole-exome sequences and whole-genome copy number variations. Results revealed heterozygous deletions of exon 6-21 of FOXP1 gene in the child. Physical examination upon admission showed that the child was generally in good condition, had a moderate nutritional status, a slightly slow response to external stimuli, equally large and equally round bilateral pupils, was sensitive to light reflection, and had poor eye contact and joint attention. He had no meaningful utterance and could not pronounce words properly. He was able to use gestures to simply express his thoughts, to perform simple actions, and to listen to instructions. He had no rash, cafe-au-lait macules, or depigmentation spots. He had thick black hair and low-set ears. He had highly sensitive skin, especially on his face and palms. He had no abnormal palm fingerprint. Cardiopulmonary and abdominal examinations revealed no abnormalities. He had normal limb muscle strength and tension. He showed normal tendon reflexes of both knees. His bilateral Babinski and meningeal irritation signs were negative. He had a normal male vulva.
Conclusion: We report the characteristic features of autism with dysphasia accompanied by mental retardation caused by FOXP1 exon deletion. This study provides a molecular basis for etiological diagnosis and treatment of the child, as well as for genetic counseling for the pedigree.
Keywords: Case report; Developmental retardation; FOXP1; Genetic expression; Mental retardation.
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