Prevalence and clinical characteristics of incontinentia pigmenti: a nationwide population-based study.

BACKGROUND

Incontinentia pigmenti (IP) is an X-linked dominant multisystemic disorder caused by pathogenic variants in the IKBKG gene. Population-based research into the epidemiology of IP is lacking.

METHODS

This nationwide cross-sectional study from Jan 1st, 1995 to August 25th, 2021, searched the Danish National Patient Registry (DNPR), the Danish National Database of Rare Genetic Diseases (RareDis) and the Danish Genodermatosis Database to identify patients recorded with a diagnosis of IP. This search was followed by diagnosis validation and collection of clinical data from patient medical records. We investigated the clinical characteristics and genetics of the final cohort of validated IP cases. We estimated the point prevalence in the Danish population, based on non-deceased IP patients currently living in Denmark. Furthermore, we estimated the birth prevalence from 1995 to 2020, assuming a diagnostic delay of up to six months.

RESULTS

We identified a validated cohort of 75 IP patients, including 71 (94.7%) females and 4 (5.3%) males. We estimated a birth prevalence of 2.37 (95% CI: 1.74-3.25) per 100,000 or 1 in 42,194. A total of 54 (72%) patients had a genetic diagnosis, including 39 (72.2%) with the recurrent exon 4-10 deletion and 10 (18.5%) with point mutations in IKBKG. A positive family history was reported in 53.3%. Besides the recognizable blaschkolinear skin lesions reported in 70 (93.3%) of the patients, commonly reported manifestations included the involvement of the teeth (58.7%), the central nervous system (30.7%), hair (26.7%), and eyes (22.6%), as well as nail dystrophy (16.0%).

CONCLUSIONS

We identified and characterized a nationwide population-based cohort of IP patients and report a birth prevalence of 2.37 per 100,000 live births, which is twice as high as previous estimates.