BackgroundKnowledge on the prevalence of sex chromosome abnormalities (SCAs) is limited, and delayed diagnosis or non-diagnosis of SCAs are a continuous concern. We aimed to investigate change over time in incidence, prevalence and age at diagnosis among Turner syndrome (TS), Klinefelter syndrome (KS), Triple X syndrome (Triple X) and Double Y syndrome (Double Y).MethodsThis study is a nationwide cohort study in a public health care system. The Danish Cytogenetic Central Registry (DCCR) holds information on all karyotypes performed in Denmark since 1961. We identified all individuals in the DCCR with a relevant SCA during 1961–2014; TS: n = 1156; KS: n = 1235; Triple X: n = 197; and Double Y: n = 287. From Statistics Denmark, which holds an extensive collection of data on the Danish population, complete data concerning dates of death and migrations in and out of Denmark were retrieved for all individuals.ResultsThe prevalence among newborns was as follows: TS: 59 per 100,000 females; KS: 57 per 100,000 males; Triple X: 11 per 100,000 females; and Double Y: 18 per 100,000 males. Compared with the expected number among newborns, all TS, 38% of KS, 13% of Triple X, and 18% of Double Y did eventually receive a diagnosis. The incidence of TS with other karyotypes than 45,X (P < 0.0001), KS (P = 0.02), and Double Y (P = 0.03) increased during the study period whereas the incidence of 45,X TS decreased (P = 0.0006). The incidence of Triple X was stable (P = 0.22).ConclusionsThe prevalence of TS is higher than previously identified, and the karyotypic composition of the TS population is changing. Non-diagnosis is extensive among KS, Triple X and Double Y, whereas all TS seem to become diagnosed. The diagnostic activity has increased among TS with other karyotypes than 45,X as well as among KS and Double Y.

Sex chromosome abnormalities (SCAs) are characterized by gain or loss of entire sex chromosomes or parts of sex chromosomes with the best‐known syndromes being Turner syndrome, Klinefelter syndrome, 47,XXX syndrome, and 47,XYY syndrome. Since these syndromes were first described more than 60 years ago, several papers have reported on diseases and health related problems, neurocognitive deficits, and social challenges among affected persons. However, the generally increased comorbidity burden with specific comorbidity patterns within and across syndromes as well as early death of affected persons was not recognized until the last couple of decades, where population‐based epidemiological studies were undertaken. Moreover, these epidemiological studies provided knowledge of an association between SCAs and a negatively reduced socioeconomic status in terms of education, income, retirement, cohabitation with a partner and parenthood. This review is on the aspects of epidemiology in Turner, Klinefelter, 47,XXX and 47,XYY syndrome.

The first estimate on prevalence of 46,XY females is 6.4 per 100 000 live born females. The presentation of AIS and gonadal dysgenesis is distinctly different, with AIS being diagnosed during childhood and gonadal dysgenesis during pubertal years. The presenting phenotype is dependent on the cause of 46,XY DSD.

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Objective: Although the overall risk of cancer is not increased in Turner syndrome, the pattern of cancer occurrence differs from the general population. We aim to describe the cancer morbidity pattern in Turner syndrome and evaluate the effect of long-term hormone replacement therapy (HRT). Design: Nationwide epidemiological study. Methods: 1,156 females with Turner syndrome diagnosed during 1960-2014, were linked with data from the Danish National Patient Registry. Statistics Denmark randomly identified 115,578 female controls. Stratified Cox regression was used to analyze cancer morbidity, mortality and effect of HRT. Results: Overall risk of cancer was not elevated (Hazard ratio 1.04 (95%CI 0.80-1.36)). The risk of skin cancer and benign skin neoplasms was two-fold increased, while the risk of breast cancer was decreased (Hazard ratio 0.4 (0.2-0.9)). Turner syndrome (45,X) had a two- to five-fold increased risk of benign central nervous system tumors, colon and rectal cancers, benign skin neoplasms and skin cancer. Turner syndrome women with a 45,X/46,XX karyotype had increased risk of tongue cancer. HRT had no impact on the risk of any cancer investigated in this study. Conclusions: The lack of one X chromosome might play a role in skin neoplasms, central nervous system tumors, colon and rectal cancers. The risk of breast cancer is lower than in the general population. Long-term HRT during the premenopausal age range seem not to exert a cancerous effect in Turner syndrome. Increased vigilance concerning specific types of cancer in Tuner syndrome harboring a 45,X karyotype is needed.