Abstract: Objective To investigate the clinical manifestations of Cantu syndrome complicated with 22q11.2 duplication syndrome and to raise awareness regarding the diagnosis of the co-occurrence of both genetic diseases. Methods Analyzing the clinical data and molecular genetic results of a patient with Cantu syndrome complicated with 22q11.2 duplication syndrome. Results The patient was an 11-year-old male who presented with chest tightness and shortness of breath for 3 days. He exhibited generalized hypertrichosis and distinctive facial features. Clinical examinations revealed that the patient had cardiac defects (patent foramen ovale and patent ductus arteriosus), tortuosity and dilation of cerebral blood vessels, and delayed bone age. Based on genetic testing, a heterozygous variant c.3605C＞T in the ABCC9 gene, confirming a diagnosis of Cantu syndrome. Additionally, a copy number duplication of approximately 2.87 Mb at the 22q11.21 chromosomal region was detected. Conclusions The 22q11.2 duplication syndrome exhibits incomplete penetrance. Its partial phenotypic overlap with Cantu syndrome pose a significant risk of missed diagnosis.

Key words: Cantu syndrome, ABCC9, 22q11.2 duplication syndrome, genetic diagnosis