What are the characteristic nail findings in iron deficiency versus calcium deficiency, and how should each deficiency be evaluated and managed?

Nail Findings in Iron Deficiency vs Calcium Deficiency

Iron deficiency causes koilonychia (spoon-shaped nails), while calcium deficiency does not cause characteristic nail changes—nail abnormalities should prompt immediate evaluation for iron deficiency with ferritin testing and gastrointestinal investigation. 1, 2

Iron Deficiency: Koilonychia (Spoon Nails)

Characteristic Features

• Thin, brittle, spoon-shaped nails with central depression and lateral eversion of the nail plate 2, 3
• Distal edges may appear rough and darkened 4
• Nails become lusterless and concave in appearance 4
• This finding indicates chronic iron deficiency secondary to malnutrition, chronic blood loss, or malabsorption 2, 3

Clinical Significance

• Koilonychia represents a late manifestation of prolonged iron depletion 2
• The presence of koilonychia should immediately prompt investigation for iron deficiency, even if hemoglobin is normal 2
• Iron deficiency can affect nail growth, skin defects, and mucosal regeneration even without frank anemia 1

Calcium Deficiency: No Specific Nail Findings

Calcium deficiency does not produce characteristic nail abnormalities. The medical literature and guidelines do not identify any specific nail changes associated with calcium or vitamin D deficiency. 1

When evaluating nail and hair anomalies, guidelines recommend checking for iron deficiency, thyroid dysfunction, and drugs as aggravating factors—notably, calcium is not mentioned as a cause of nail pathology. 1

Diagnostic Evaluation for Iron Deficiency

Initial Laboratory Testing

• Serum ferritin: <30 μg/L confirms iron deficiency without inflammation; <100 μg/L suggests deficiency when inflammation is present 5
• Transferrin saturation: <30% supports iron deficiency diagnosis 5
• C-reactive protein (CRP): Essential to interpret ferritin correctly, as inflammation elevates ferritin and can mask true deficiency 5

Critical Point About Normal Hemoglobin

• Normal hemoglobin does NOT exclude iron deficiency—it may represent early-stage deficiency or compensated iron depletion 5
• High RDW with low MCH indicates iron deficiency even with normal hemoglobin 5

Mandatory Gastrointestinal Investigation

Who Requires GI Evaluation

• All adult men and post-menopausal women with confirmed iron deficiency require gastrointestinal evaluation regardless of hemoglobin level or symptom presence 5
• GI investigations should be considered in all patients with confirmed IDA unless there is significant non-GI blood loss 1

Upper GI Evaluation

• Upper endoscopy with small bowel biopsies reveals a cause in 30-50% of patients 1, 5
• Small bowel biopsies are mandatory during endoscopy as 2-3% of patients with IDA have celiac disease 1, 5

Lower GI Evaluation

• Colonoscopy or barium enema is required even if upper GI source is found 1
• Dual pathology (lesions in both upper and lower GI tracts) occurs in approximately 10-15% of patients 1, 5
• Unless upper endoscopy reveals carcinoma or celiac disease, all patients should undergo lower GI tract examination 1

Treatment Approach

Iron Replacement

• Initiate oral iron supplementation once iron deficiency is confirmed by ferritin testing 5
• Intravenous iron is indicated if oral iron is not tolerated, ineffective, or if malabsorption is present 1
• Continue iron for 3-6 months after hemoglobin normalizes to replete stores 5

Monitoring

• Patients should be monitored for recurrent iron deficiency every 3 months for at least a year after correction 1
• Recurrent anemia may indicate persistent intestinal disease activity even with clinical remission 1

Critical Pitfalls to Avoid

• Never assume normal hemoglobin excludes significant pathology—pre-anemic iron deficiency can indicate serious underlying disease including malignancy 5
• Do not accept superficial findings (esophagitis, erosions, peptic ulcer) as the sole cause without completing lower GI evaluation 1
• Avoid empiric iron therapy without confirming iron deficiency, as this can cause harm in thalassemia patients and delays proper diagnosis 5
• Do not attribute nail changes to calcium deficiency—this is not supported by evidence and will delay diagnosis of iron deficiency 1, 2