The effect of vitamin D recommendations on serum 25-hydroxyvitamin D level in erythropoietic protoporphyria patients

Abstract Objectives Erythropoietic protoporphyria (EPP) patients avoid sun exposure due to photosensitivity. For decades, sun-avoiding Danes are recommended daily vitamin D supplements all year. We offered our EPP patients, serum 25-hydroxyvitamin D (25(OH)D) monitoring, and counselling if their level was low. We aimed to investigate the effect of the general recommendation and counselling on 25(OH)D status in patients attending our clinic. Additionally, the 25(OH)D status of our EPP patients were compared to British EPP patients not taking vitamin D supplements, and that of the general Danish population. Methods Forty-six Danish EPP patients had 25(OH)D measured in 721 blood samples collected between 2003 - 2021. Dates of individual counselling were noted. Data on British EPP patients and the general Danish population were extracted from previous publications. Results Our patients had higher 25(OH)D levels than British EPP patients not taking vitamin D supplements, but the recommendations did not elevate their 25(OH)D level to that of the general Danish population. Overall, 17.5% of the 25(OH)D measurements in Danish EPP patients were below 30 nmol/L (deficiency) and 29.4% were between 30 nmol/L and 50 nmol/L (insufficiency). Patients were monitored for a median of 11 years. Thirty-one patients had a total of 74 vitamin D counselling sessions providing an increase in 25(OH)D of about 18 nmol/L the year after. However, many patients repeatedly developed insufficiency. Conclusions This study documents the positive effect of vitamin D recommendations on serum 25(OH)D in patients with EPP. Follow-up on vitamin D status and recommendations is essential to increase 25(OH)D levels.