[A case of intellectual developmental disorder with behavioral abnormalities and craniofacial dysmorphism with or without seizures caused by PHF21A gene variation and review of literature].

Objective: To discuss the clinical and genetic features of intellectual developmental disorder with behavioral abnormalities and craniofacial dysmorphism with or without seizures (IDDBCS). Methods: The clinical and genetic records of a patient who was diagnosed with IDDBCS caused by PHF21A gene variation at Children's Hospital Capital Institute of Pediatrics in 2021 were collected retrospectively. Using " PHF21A gene" as the keyword, relevant articles were searched at CNKI, Wanfang Data and PubMed from establishment of databases to February 2023. Clinical and genetic features of IDDBCS were summarized in the combination of this case. Results: An 8 months of age boy showed overgrowth (height, weight and head circumference were all higher than the 97^th percentile of children of the same age and sex) and language and motor developmental delay after birth, and gradually showed autism-like symptoms like stereotyped behavior and poor eye contact. At 8 months of age, he began to show epileptic seizures, which were in the form of a series of spastic seizures with no reaction to adrenocorticotropic hormone but a good response to vigabatrin. Physical examination showed special craniofacial appearances including a prominent high forehead, sparse eyebrows, broad nasal bridge, and downturned mouth with a tent-shaped upper lip. The patient also manifested hypotonia. Whole exome sequencing showed a de novo heterogeneous variant, PHF21A (NM_001101802.1): c.54+1G>A, and IDDBCS was diagnosed. A total of 6 articles (all English articles) were collected, involving this case and other 14 patients of IDDBCS caused by PHF21A gene variation. Clinical manifestations were intellectual disability or developmental delay (15 patients), craniofacial anomalies (15 patients), behavioral abnormalities (12 patients), seizures (9 patients), and overgrowth (8 patients). The main pathogenic variations were frameshift variations (8 patients). Conclusions: IDDBCS should be considered when patients show nervous developmental abnormalities, craniofacial anomalies, seizures and overgrowth. PHF21A gene variation detection helps to make a definite diagnosis.