Bone mineral density and vitamin D levels in erythropoietic protoporphyria

Abstract

Erythropoietic protoporphyria (EPP) is a rare disease with painful cutaneous photosensitivity, in which patients are recommended to avoid sun exposure, and wear sunscreen and adequate clothing. Our aim was to study bone mineral density (BMD) and other mineral parameters, including serum 25(OH)D levels, to evaluate the impact of these measures in the follow-up of EPP patients. A cross-sectional study of ten EPP patients (median age 25; range 22-55, four males and six females), was performed evaluating clinical features, biochemical values (bone markers and serum 25 hydroxyvitamin D), and BMD. Median serum 25(OH)D level was 19.65 ng/ml [17.50; 24.80]. Four patients had 25(OH)D in insufficiency range (20-30 ng/ml) and five patients in the deficiency range (<20 ng/ml). Lumbar T-score median levels were in the osteopenia range in both females (-1.50 [-2.30; -1.0]) and males (-1.90 [-2.40; -0.70]). Also, in the female group median femoral neck T-score were in the osteopenia range (-1.20 [-1.60; -0.60]). This is the first study reporting low BMD in EPP patients. Osteoporosis, osteopenia, and vitamin D deficiency are frequent findings in EPP patients. The contribution of sunlight avoidance measures to these results remains to be clarified. Serum levels of protoporphyrins were not related to these alterations and other factors should be investigated. We suggest that the monitoring of serum vitamin D levels in EPP patients should be mandatory, as well as vitamin D and calcium supplementation.