Serum Immunoglobulins in Children with Vitamin D Resistant Rickets Ezzat K. Amin, Hossam Kamal, Ahmed Gab-Allah, Seham Alzarrouq, Mohamed A Talat Suez Canal University Medical Journal, October 2019, Vol. 22(2), Pages 157-163. Background: Vitamin D plays an immunoregulatory role in both the innate and adaptive immune systems. Rickets is a disorder that can develop due to a lack of vitamin D, calcium, or phosphate. Aim: The aim of this study was to assess serum immunoglobulins as one of the aspects of humoral immunity in children with vitamin D resistant rickets. Subjects and Methods: This case-control study was performed on 60 patients divided into Group (A):30 cases with vitamin D resistant rickets patients who were presented with rachitic manifestation who didn’t respond to therapeutic doses of the vitamin. Group (B):30 cases with untreated classic vitamin D deficiency rickets. Group (C): 30 healthy subjects as a control group. All subjects were subjected to detailed history taking including age, sex, weight, dietary history, medication history, and physical examination including vital signs, body weight, and head circumference. Laboratory investigations that included calcium, phosphorus, alkaline phosphatase, electrolytes, ESR, urine analysis, parathyroid hormone, vitamin D, and Immunoglobulin assay. Results: There is a significant decrease of IgA in vitamin D deficiency rickets and vitamin D resistant rickets than in controls (3.74 ± .867, 3.13 ± 1.72, 5.01 ± 1.61, respectively with P =0.012).There is a significant decrease of IgG in vitamin D deficiency rickets and a significant increase in vitamin D resistant rickets than in controls (523.5 ± 136.3, 751.25 ±163.5, 692.0 ± 186.4, respectively with P =0.009). There is no significant difference in IgM in the three studied groups. Conclusion: Patients with vitamin D deficiency have significantly lower IgG levels, while vitamin D resistant patients have significantly higher IgG levels. Whereas, both groups have lower IgA and normal IgM levels.