ABSTRACT
INTRODUCTION: Klinefelter syndrome (KS), a sex chromosome aneuploidy, is associated with a 47,XXY chromosomal complement and is diagnosed in â¼1:600 live male births. Individuals with a 46,XX cell line in addition to 47,XXY are less common with a limited number of published case reports. METHODOLOGY: To better understand the implications of a 47,XXY/46,XX karyotype, we conducted a retrospective, multi-center analysis of the cytogenetic findings and associated clinical records of 34 patients diagnosed with this SCA across 14 institutions. RESULTS: Presence of the XX cell line ranged from 5-98% in patient specimens. Phenotypes also exhibited significant heterogeneity with some reporting a single reason for referral and others presenting with a constellation of symptoms, including ambiguous genitalia and ovotestes. Ovotestes were present in 12% of individuals in this cohort, who had a significantly higher percentage of XX cells. Notably, two patients were assigned female sex at birth DISCUSSION: These findings highlight the variability of the clinical phenotypes associated with this SCA as well as the challenges of clinical management for this population. Karyotype or FISH analysis, which offer single-cell resolution, rather than chromosomal microarray or molecular testing, is the ideal test strategy in these instances as mosaicism can occur at low levels.
