Vitamin D deficiency in sickle cell disease: a neglected comorbidity in Tunisia.

Sickle cell disease (SCD) is a hereditary hemoglobinopathy that imposes a significant burden on global health. Individuals with SCD often experience multiple nutritional deficiencies, among which vitamin D deficiency has emerged as a critical yet under recognized factor contributing to disease complications. This study aimed to assess the vitamin D status in patients with SCD compared to a matched healthy control group, and to explore its correlation with clinical and biological parameters, including the frequency of vaso-occlusive crises (VOC). A cross-sectional study was conducted between January and June 2024 at Bechir Hamza Children's Hospital, Tunis. Sixty-four SCD patients and 63 healthy controls were enrolled. Vitamin D [25(OH)D] levels, along with hematologic and biochemical markers, were measured. Statistical analyses included t-tests, chi-square test, ANOVA, and Spearman correlation. Vitamin D levels were significantly lower in the SCD group (15.05 ± 6.6 ng/mL) compared to controls (22.51 ± 12.54 ng/mL, p = 0.026). Among SCD patients, 78.2% (50) had Vitamin D deficiency (< 20ng/mL), 20.3% (13) had Vitamin D insuffisancy (20-30 ng/mL) and only one patient (1.5%) had normal vitamin D status (> 30 ng/mL). Vitamin D levels were inversely correlated with age, total bilirubin, parathyroid hormone (PTH), and frequency of VOC, and positively correlated with hemoglobin concentration and socioeconomic status. SCD patients with vitamin D deficiency experienced significantly more VOC episodes per year. Vitamin D deficiency is highly prevalent among SCD patients and is associated with increased disease severity. Routine screening and appropriate supplementation should be considered as part of comprehensive SCD management strategies.