Jennifer Phan^{1, 2}, Ellie Wu¹, Kasey Peachy¹, Renata Bird¹, Niamh Hewitt¹, Jillian Nicholl¹, Kathryn Friend¹, Carol Siu¹, Sui Yu¹

¹Department of Genetics and Molecular Pathology, SA Pathology, Adelaide, SA, Australia; ² Genomics, Pathology Queensland, Herston, QLD, Australia.

Our case involves a 10-year-old female who was referred for SNP microarray and Fragile X testing as part of routine autism spectrum disorder (ASD) work up. No clinically significant copy number variants were detected on SNP microarray, and Fragile X repeat expansion testing detected a single peak in the normal repeat range with no evidence of an expanded allele. However, SNP microarray detected an unexpected XY sex chromosome complement.

Sex mismatches can be the result of laboratory technical errors or biological causes. A thorough laboratory investigation was performed, including additional testing and a sample recollection, to rule out a laboratory technical error. Discussion with the referring paediatrician did not reveal any significant clinical history that provided a biological cause for the sex mismatch. The patient was referred to paediatric endocrinology for further work up, and a disorders of sex development (DSD) gene panel was performed. A hemizygous Likely Pathogenic variant in the androgen receptor (AR) gene was detected, which confirmed a diagnosis of complete androgen insensitivity syndrome. This is a rare case of an incidental finding of DSD in a pre-pubertal patient and highlights the potential complexity that can occur with genome-wide testing.