Molecular Karyotyping in Children and Adolescents with Gender Dysphoria

Purpose: The presence of a disorder of sexual development (DSD) acts as a diagnostic specifier for gender dysphoria (GD) under DSM-5, while the International Classification of Diseases (ICD)-10 specifically states that its equivalent diagnosis, gender identity disorder (GID), must not be the result of a chromosomal abnormality. For these reasons, routine karyotyping has been previously advocated in the clinical work-up of children and adolescents with suspected GD or GID. However, the utility of such testing remains unclear. Methods: The results of routine molecular karyotyping were analyzed in 128 patients attending our Australian statewide pediatric gender service from 2013 to 2016. Karyotyping was performed using an Illumina BeadChip platform and provided information on both sex chromosome composition and copy number variation (CNV). Results: No sex chromosome abnormalities directly suggestive of a DSD were discovered. The rate of CNVs among our patient cohort was 8.6% (11/128), similar to that previously reported for the general population. Unexpectedly, three trans male patients shared the same CNV, involving an almost identical 400 kbp deletion on chromosome 15q11.2. The frequency of this deletion within birth-assigned females in our cohort (3/69; 4.3%) was significantly higher than that within local control populations (0.3%; Fisher's exact test p-value=0.002), suggesting a possible association between 15q11.2 deletions and trans male identity. Conclusion: Routine molecular karyotyping failed to detect any occult DSD and indicated that the rate of CNVs was similar to that of the general population. Given these findings, we suggest that molecular karyotyping has minimal clinical utility in the routine management of children and adolescents with GD.