A National Epidemiological Study of Inherited Ichthyoses in England from 1998-2024.

Abstract

Ichthyoses cause significant morbidity and mortality, however national epidemiological data that link diagnoses of ichthyoses with systemic comorbidities are lacking. Report epidemiological data on inherited ichthyoses in England, together with patient level comorbidities and genetic testing status. This national retrospective cohort study identified ichthyosis case records from healthcare databases in England, using ICD-10 codes from 1998-2024. Cohort demographics, comorbidities, genetic testing data, and mortality data were extracted from routinely collected NHS data. We identified 4330 ichthyosis patients, of which 3758 were categorised as having a rare ichthyosis. Prevalence of the rare ichthyoses was 51.6 per million [95% CI 49.7-53.5]. Compared to the reference population, the overall cohort was younger (median age 22 (interquartile range 38) vs. 41 years), more likely to identify as Asian (17.1% vs 9.6%, P < 0.001), and more frequently in the most deprived quintiles (48.1% vs 40%, P < 0.001). Rates of comorbidities including asthma, inflammatory arthropathies and atrial fibrillation were higher than in the reference population. 18.5% of deaths occurred before 25 years of age compared with 1% of deaths at this age threshold in the reference population (P < 0.001). Genetic testing data revealed a low proportion of tested cases; pathogenic variants in genes known to cause ichthyosis were found in 90 (56%) of the 160 tested cases. We report an increased range of comorbidities in patients living with rare ichthyoses, highlighting the systemic burden in patients categorised as having non-syndromic ichthyosis. These data inform healthcare planning, research design and the redressing of inequities of care.