Investigating the role of vitamin D levels and clinical, laboratory findings, prognosis, and treatment response in patients with immune hemolytic anemia and immune thrombocytopenic purpura

Introduction and Objective: Corticosteroids are used as the first-line treatment for life-threatening immunological hematologic diseases such as immune thrombocytopenic purpura (ITP) and immune hemolytic anemia (IHA). In cases of steroid resistance, immunosuppressive agents such as eltrombopag, splenectomy, rituximab, and azathioprine can be administered as second-line therapies. Vitamin D, whose effects on innate and adaptive immune cells have been demonstrated in various studies, is thought to play a role in treatment resistance in autoimmune diseases through several mechanisms. While its effects on calcium metabolism are well known, studies investigating its anti-inflammatory and immunomodulatory efficacy are ongoing. This study aimed to investigate the effect of vitamin D levels on clinical and laboratory findings, prognosis, and treatment response in patients diagnosed with immune hemolytic anemia and immune thrombocytopenic purpura. Materials and Methods: Patients diagnosed with ITP and IHA who were evaluated in the hematology ward and outpatient clinic between January 2012 and January 2025 were retrospectively analyzed. Demographic data (age, sex), medical history, laboratory parameters (glucose, urea, creatinine, uric acid, AST, ALT, ALP, GGT, total bilirubin, indirect bilirubin, LDH, albumin, CRP, procalcitonin, total cholesterol, HDL, LDL, triglycerides, folic acid, vitamin B12, ferritin, vitamin D, parathormone, HbA1C, PT, APTT, INR, fibrinogen), imaging findings (abdominal and thyroid ultrasonography), comorbidities before and at diagnosis, medications used, treatments received, treatment responses, and overall survival data were collected retrospectively from the hospital information management system. Results: A total of 206 patients were included in the study, comprising 83 with IHA and 123 with ITP. Among IHA patients, 37.3% had vitamin D deficiency and 41% had vitamin D insufficiency; among ITP patients, 30.9% had vitamin D deficiency and 43.9% had vitamin D insufficiency. When compared with the national average reported by Turkish Endocrinology and Metabolism Association, the proportion of patients in our study requiring vitamin D replacement is similar to the Turkish average. No significant relationship was found between vitamin D levels and sex or age; however, IHA patients were significantly older than ITP patients. Although there was no significant difference in body mass index (BMI) between the two groups, an inverse relationship between BMI and vitamin D levels was observed in IHA patients (p = 0.032). We found no statistically significant difference between vitamin D levels and hemogram parameters, routine biochemical tests, vitamin B12, folic acid, ferritin, or coagulation values. However, there was a significant difference between parathormone levels according to vitamin D categories (p< 0.05); patients with vitamin D levels below 10 ng/mL had significantly higher parathormone levels, as expected. Immune thrombocytopenic purpura patients experienced significantly more disease relapses than IHA patients (p< 0.01). While no correlation was found between vitamin D levels and relapse frequency in IHA patients, in ITP patients, relapse frequency differed significantly by vitamin D category: patients with vitamin D <10 ng/mL had more relapses than those with vitamin D >20 ng/mL (p = 0.028). No statistically significant difference was found in hospital stay duration according to vitamin D levels, and no difference was observed between IHA and ITP groups regarding hospitalization time (p=0.133). The mean follow-up duration was 30.4 months (median 14) for IHA patients and 56.5 months (median 39) for ITP patients, indicating that ITP patients were followed longer (p<0.01). No correlation was found between vitamin D levels and follow-up duration. In terms of survival, ITP patients had significantly longer survival times compared to IHA patients (p<0.01). In both groups, patients with vitamin D <10 ng/mL had shorter survival. Further analysis revealed that vitamin D was not an independent variable affecting mortality. In IHA patients, advanced age and the presence of comorbidities were associated with increased mortality (p<0.05), while in ITP patients, no independent variable significantly affected mortality. Conclusion: Vitamin D deficiency is quite common in patients with immune hemolytic anemia and immune thrombocytopenic purpura. Low vitamin D levels, particularly in ITP patients, were associated with increased relapse frequency and higher treatment requirements. Considering the role of vitamin D in immune regulation, measuring vitamin D levels at the time of diagnosis and correcting possible deficiencies may enhance treatment success. Larger prospective studies evaluating immunologic markers in greater detail will provide more conclusive evidence regarding the relationship between vitamin D and these two diseases.