Vitamin D deficiency rickets: This condition is characterized by vitamin D insufficiency, which can lead to low calcium levels, bone pain, and potentially normocytic anemia due to the impact of vitamin D on erythropoiesis and bone marrow function. The presence of vitamin D insufficiency and low calcium levels strongly supports this diagnosis.

Chronic kidney disease (CKD): CKD can cause normocytic anemia due to decreased erythropoietin production, bone pain from secondary hyperparathyroidism, and abnormalities in calcium and vitamin D metabolism. However, CKD would typically present with other abnormalities such as elevated creatinine levels, which are not mentioned.
Inflammatory conditions (e.g., chronic infections, autoimmune diseases): These conditions can cause normocytic anemia, elevated WBC count, and bone pain. Vitamin D insufficiency is common in chronic diseases due to various factors including reduced sun exposure and dietary intake.

Leukemia or lymphoma: Although less likely, these malignancies can present with normocytic anemia, elevated WBC count, bone pain, and may have associated vitamin D insufficiency. Missing these diagnoses could be fatal, making them crucial to rule out.
Multiple myeloma: This condition can cause normocytic anemia, bone pain, and elevated calcium levels (though low calcium is mentioned, myeloma can have variable effects on calcium). Vitamin D insufficiency is common in myeloma patients.

Osteogenesis imperfecta: A genetic disorder characterized by bone fragility and blue sclerae, which could explain bone pain. However, it does not directly explain the hematologic findings or vitamin D insufficiency.
Idiopathic hyperphosphatasia: A rare condition that affects bone metabolism and could potentially explain some of the findings, though it is quite rare and not directly linked to normocytic anemia or vitamin D insufficiency.