Excessive scarring from keloids and hypertrophic scars is associated with an increased risk for atopic eczema, investigators reported in a study published JAMA Dermatology.
Researchers used data from the UK Biobank, a large population-based prospective cohort study, to assess disease associations with keloids or hypertrophic scars. UK Biobank recruited more than 500,000 participants 40 to 69 years of age from 2006 through 2010.
Multivariable logistic regression analyses were conducted for previously studied comorbidities across several ethnic groups, and a phenome-wide association study (PheWAS) was performed for a wide range of systematically defined diseases.
Excessive scarring was the exposure variable in each analysis model, and the comorbidity studied (hypertension, uterine leiomyoma, vitamin D deficiency, and atopic eczema) was the outcome.
A total of 230,078 participants were assessed (mean [SD] age, 64  years; 54.7% women; 94.9% White), of whom 972 had a record of excessive scarring — 740 with a diagnostic code specific for keloid, 110 specific for hypertrophic scar, and 177 for either keloid or hypertrophic scar. The prevalence of excessive scarring was 1.1% for Asians, 2.4% for Blacks, and 0.4% for Whites. Among those with excessive scars, a higher percentage of women was observed compared with the unaffected group (65% vs 55%) and a lower percentage with self-reported White ethnicity (86% vs 95%).
Statistically significant associations with excessive scarring were found for hypertension and atopic eczema in the minimally adjusted models; the association with vitamin D deficiency did not achieve Bonferroni-corrected significance (odds ratio [OR], 1.42; 95% CI, 1.05-1.93; P =.02). Only the association with atopic eczema (OR, 1.68; 95% CI, 1.36-2.07; P <.001) remained significant in fully adjusted models. No significant association was found between excessive scarring and uterine leiomyoma, although a positive effect-size estimate was observed (OR, 1.19; 95% CI, 0.95-1.49; P =.13).
Associations with hypertension and uterine leiomyoma were nominally significant among Black patients (OR, 2.05; 95% CI, 1.13-3.72; P =.02 [hypertension] and OR, 1.93; 95% CI, 1.00-3.71; P =.05 [uterine leiomyoma]) and were not significant in Asian or White patients. Vitamin D deficiency was only significantly associated with excessive scarring among Asians (OR, 2.24; 95% CI, 1.26-3.97; P =.006).
The association with excessive scarring for atopic eczema was highly significant in White participants (OR, 1.68; 95% CI, 1.34-2.12; P <.001) and nominally significant in Asians (OR, 2.17; 95% CI, 1.01-4.67; P =.048).
Investigators also screened 1518 phecodes in 17 disease groups and identified 110 diseases significantly associated with excessive scarring, with the strongest association for several dermatologic diseases, most prominently sebaceous cyst (OR, 2.56; 95% CI, 2.17-3.03; P =9.45×10−30). Strong evidence for an association also was found for pain-related symptoms, especially joint pain (OR, 1.84; 95% CI, 1.61-2.1; P =1.87×10−20), as well as back pain, cervicalgia, enthesopathies, and mastodynia (all OR >1.6 and P <1.0×10−12). Statistically significant associations were found for skin cancers (melanoma, OR, 3.17; 95% CI, 2.24-4.50; P =3.33×10−11).
Study limitations include the relatively small sample size of participants with excessive scarring. Also, because most patients reported White ethnicity, the main findings, especially those from the PheWAS, may not be generalizable to other ethnic groups.
“We report a comprehensive observational analysis of a heterogeneous cohort of UK Biobank participants with excessive scarring, replicating previously reported disease associations for excessive scarring with atopic eczema and hypertension,” stated the researchers. “Only the association with atopic eczema showed a similar trend across the 3 major ethnic subgroups (Asian, Black, and White participants).”
Ung CY, Warwick A, Onoufriadis A, et al. Comorbidities of keloid and hypertrophic scars among participants in UK Biobank. JAMA Dermatol. Published online January 4, 2023. doi:10.1001/jamadermatol.2022.5607