Aim: To study prevalence, incidence, age at diagnosis, and mortality in Turner syndrome (TS) in Denmark.

Methods: Using the Danish Cytogenetic Register we identified all cases (n = 781) of TS alive in Denmark during 1970-2001. Sixty-nine deceased women with TS were identified in the Causes of Death Register. We divided the cohort into women having the karyotype 45,X, karyotypes including an isochromosome Xq, and all other karyotypes associated with TS. We describe the number of patients diagnosed in Denmark yearly, incidence rates, and the age at diagnosis. Standardized mortality ratios (SMR) were calculated.

Results: 349 women had a 45,X karyoype, 86 had a karyotype including an isochromosome Xq (isoXq), and 346 had another TS karyotype. Mortality was increased in TS with a SMR of 2.86 (95% CI: 2.18 - 3.55). SMR was increased for coronary diseases; congenital malformations; endocrine diseases; and "other causes". The mortality was increased for all types of karyotypes in comparison with the general population, but highest among females with 45,X and isoXq. There was a steady increase in prevalence, but incidence was unchanged. Age at diagnosis was mainly distributed in three periods; less than one year of age (14.9%), during adolescence (10-17 yr) (33.2%), and during adulthood (38.5%), with a median age at diagnosis of 15.1 yr, decreasing during the study period (P < 0.01).

Conclusions: Patients with TS and especially the karyotype 45,X and isoXq have a higher mortality compared with the background population. TS was diagnosed with a considerable diagnostic delay. Prevalence is increasing, but incidence of TS was stable.