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

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±18·5nmolL(-1) ) and normal AA subjects (54·8±21·2 nmolL(-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±21·0nmolL(-1) ) and normal C/H subjects (70·5±27·4nmolL(-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.