What is the appropriate diagnosis and treatment plan for a patient with anemia, hypocalcemia, and normal kidney function?

Diagnostic Assessment and Treatment Plan

This patient requires urgent evaluation for vitamin B12 deficiency and hypocalcemia, with immediate supplementation of both deficiencies while investigating the underlying cause of anemia through complete iron studies and gastrointestinal evaluation.

Immediate Diagnostic Priorities

Anemia Workup

• The RBC count of 4.25 million/μL with B12 of 134 pg/mL (low) indicates probable B12 deficiency anemia, which requires immediate treatment 1, 2
• Complete iron studies are mandatory, including serum ferritin and transferrin saturation (TSAT), as the TIBC of 210 μg/dL (low-normal) suggests possible functional iron deficiency 1
• A reticulocyte count is essential to assess bone marrow response and distinguish between hypoproliferative versus hemolytic causes 3
• Peripheral blood smear examination should be performed to evaluate red cell morphology and confirm macrocytic changes expected with B12 deficiency 3

Hypocalcemia Evaluation

• Calcium of 7.6 mg/dL represents significant hypocalcemia requiring urgent correction, particularly given the low albumin of 3.2 g/dL 3
• Calculate corrected calcium: Corrected Ca = 7.6 + 0.8 × (4.0 - 3.2) = 8.2 mg/dL, which still indicates true hypocalcemia 3
• Measure intact parathyroid hormone (PTH), 25-hydroxyvitamin D, phosphorus, and magnesium levels to determine etiology 3
• The combination of anemia and hypocalcemia may indicate B12 deficiency as a contributing factor, as documented in case reports 4

Hypoalbuminemia Investigation

• Total protein 5.6 g/dL with albumin 3.2 g/dL indicates significant protein malnutrition or loss, requiring evaluation for malabsorption, protein-losing enteropathy, or chronic inflammation 1
• This hypoalbuminemia may contribute to hypocalcemia and suggests underlying gastrointestinal pathology 2

Urgent Gastrointestinal Evaluation Required

• All patients with unexplained B12 deficiency and hypoalbuminemia require bidirectional endoscopy to exclude gastrointestinal malignancy or malabsorption syndromes 2
• Approximately one-third of patients with nutritional deficiencies have underlying gastrointestinal pathology requiring urgent diagnosis 2
• Evaluate for pernicious anemia with anti-intrinsic factor antibodies and anti-parietal cell antibodies 4
• Consider celiac disease screening with tissue transglutaminase antibodies given the constellation of nutritional deficiencies 1

Immediate Treatment Plan

Vitamin B12 Replacement

• Initiate intramuscular cyanocobalamin 1000 μg daily for 1 week, then weekly for 4 weeks, then monthly indefinitely for severe B12 deficiency 3
• Oral B12 supplementation (1000-2000 μg daily) is inadequate given the severity of deficiency and likely malabsorption 3
• Monitor hemoglobin weekly initially, as reticulocytosis should occur within 3-7 days if B12 deficiency is the primary cause 1

Calcium Correction

• Administer elemental calcium 1-2 grams daily in divided doses between meals for symptomatic hypocalcemia 3
• If corrected calcium remains <8.5 mg/dL after addressing phosphorus, increase calcium supplementation 3
• Measure 25-hydroxyvitamin D; if <30 ng/mL, provide vitamin D2 50,000 units orally monthly for 6 months 3
• Monitor for symptoms of severe hypocalcemia (paresthesias, tetany, seizures) which may require intravenous calcium gluconate 3

Iron Assessment and Replacement

• Once ferritin and TSAT results are available, if ferritin <100 μg/L or TSAT <20%, initiate iron replacement 1
• Intravenous iron is strongly preferred over oral iron given multiple nutritional deficiencies, likely malabsorption, and hypoalbuminemia 1
• Oral iron (100-200 mg elemental iron daily) may be considered only if IV access is problematic and gastrointestinal tolerance is confirmed 2

Critical Monitoring Parameters

• Hemoglobin should be monitored weekly until stable after B12 replacement, then monthly 1
• Recheck calcium, albumin, and phosphorus within 1-2 weeks after initiating supplementation 3
• Repeat B12 level after 1 month of replacement to confirm adequate response 3
• Monitor for reticulocytosis within 3-7 days as evidence of bone marrow response to B12 therapy 3

Common Pitfalls to Avoid

• Do not delay B12 replacement while awaiting endoscopy results, as neurologic complications can become irreversible 3
• Avoid using hematocrit instead of hemoglobin for monitoring, as hematocrit is less reproducible and affected by storage time 3
• Do not assume normal kidney function (GFR 90) excludes CKD-related anemia; the combination of nutritional deficiencies may mask early CKD 3
• Never initiate erythropoiesis-stimulating agents before correcting nutritional deficiencies and excluding malignancy 1
• Folate level of 6.8 ng/mL is adequate; avoid empiric folate supplementation without documented deficiency, as it may mask B12 deficiency 3

Nephrology Referral Considerations

• While GFR is currently 90 mL/min/1.73 m², the combination of anemia, hypocalcemia, and hypoalbuminemia warrants nephrology consultation if these abnormalities persist after nutritional repletion 3
• If hemoglobin remains low after 8-12 weeks of B12 and iron replacement, consider CKD as a contributing factor requiring erythropoietin evaluation 3