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

BACKGROUND: Ichthyoses cause significant morbidity and mortality, however national epidemiological data that link diagnoses of ichthyoses with systemic comorbidities are lacking. OBJECTIVE: Report epidemiological data on inherited ichthyoses in England, together with patient level comorbidities and genetic testing status. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.