25-hydroxyvitamin D levels in African-American and Caucasian/Hispanic subjects with cutaneous lupus erythematosus

Summary Background Because exposure to ultraviolet radiation accounts for a significant portion of endogenous vitamin D production, subjects with cutaneous lupus (CLE) who practise sun-protective measures are at risk for vitamin D insufficiency. Previous studies have shown light-skinned subjects with CLE to have lower serum 25-hydroxy (25-OH) vitamin D levels than normal controls. Objectives To assess the status of vitamin D insufficiency in dark-skinned individuals with CLE. Methods We performed a cross-sectional study comparing serum 25-OH vitamin D levels in 25 African-American (AA) subjects with CLE and 26 normal AA subjects matched by age, sex and season in Dallas, Texas. A questionnaire on demographics, medical history and lifestyle habits was administered to determine factors potentially affecting vitamin D levels. Findings were contrasted to a similar comparison in 26 Caucasian and Hispanic (C/H) subjects with CLE and 24 normal C/H subjects matched by age, sex and season. Results We found similar mean ± SD 25-OH vitamin D levels in AA subjects with CLE (52·0 ± 18·5 nmol L ^-1) and normal AA subjects (54·8 ± 21·2 nmol L ^-1) (P = 0·62). Almost half of AA subjects in both groups were vitamin D insufficient. A larger difference in 25-OH vitamin D levels was found between C/H subjects with CLE (59·4 ± 21·0 nmol L ^-1) and normal C/H subjects (70·5 ± 27·4 nmol L ^-1) (P = 0·12). Two-way anova demonstrated that skin colour (AA vs. C/H) had a significant effect on 25-OH vitamin D levels (P = 0·008), although CLE status (CLE vs. normal) did not (P = 0·13). Conclusions Providers are encouraged to address vitamin D insufficiency concerns in all dark-skinned individuals. Future studies should stratify subjects by skin colour in determining differences between subjects with CLE and normal controls.