Monosomy 1p36 syndrome is the most commonly observed subtelomeric deletion syndrome. Patients with this syndrome typically have common clinical features, such as intellectual disability, epilepsy, and characteristic craniofacial features. Method: In cooperation with academic societies, we analyzed the genomic copy number aberrations using chromosomal microarray testing. Finally, the genotype-phenotype correlation among them was examined. Results: We obtained clinical information of 86 patients who had been diagnosed with chromosomal deletions in the 1p36 region. Among them, blood samples were obtained from 50 patients (15 males and 35 females). The precise deletion regions were successfully genotyped. There were variable deletion patterns: pure terminal deletions in 38 patients (76%), including three cases of mosaicism; unbalanced translocations in seven (14%); and interstitial deletions in five (10%). Craniofacial/skeletal features, neurodevelopmental impairments, and cardiac anomalies were commonly observed in patients, with correlation to deletion sizes. Conclusion: The genotype-phenotype correlation analysis narrowed the region responsible for distinctive craniofacial features and intellectual disability into 1.8-2.1 and 1.8-2.2. Mb region, respectively. Patients with deletions larger than 6.2. Mb showed no ambulation, indicating that severe neurodevelopmental prognosis may be modified by haploinsufficiencies of KCNAB2 and CHD5, located at 6.2. Mb away from the telomere. Although the genotype-phenotype correlation for the cardiac abnormalities is unclear, PRDM16, PRKCZ, and RERE may be related to this complication. Our study also revealed that female patients who acquired ambulatory ability were likely to be at risk for obesity.
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