What is the approach to managing generalized itch in a vegetarian patient with iron deficiency anemia?

Differential Diagnosis and Management of Generalized Itch in a Vegetarian with Iron Deficiency Anemia

Iron deficiency anemia is the most common cause of generalized pruritus in patients with underlying systemic disease (25% of cases), and iron replacement therapy should be initiated immediately as it can lead to complete cessation of pruritus shortly after commencement. 1

Primary Diagnosis: Iron Deficiency-Related Pruritus

The vegetarian diet is a critical clue here, as dietary iron deficiency is a leading cause of iron deficiency anemia in this population. 1 The British Association of Dermatologists guidelines specifically emphasize inquiring about vegetarian or vegan diets when evaluating generalized pruritus without rash. 1

Immediate Diagnostic Workup

Check the following labs in all patients with generalized pruritus without rash: 1

• Complete blood count - looking for anemia and microcytosis
• Ferritin levels - note that ferritin is an acute-phase protein and may be falsely elevated even with iron deficiency 1
• Serum iron and total iron binding capacity - if ferritin appears "normal" but iron deficiency is still suspected 1
• Tissue transglutaminase (TTG) antibodies - essential in vegetarians with unexplained iron deficiency to rule out celiac disease 1
• IgA levels - because IgA deficiency can cause falsely negative TTG readings 1

Critical Celiac Disease Consideration

In vegetarians with unexplained iron deficiency, celiac disease must be excluded as it is present in 2-6% of asymptomatic patients with iron deficiency anemia. 1 The patient should not have been excluding gluten for at least 6 weeks before TTG testing. 1 If TTG is abnormal, refer to gastroenterology for endoscopy and small bowel biopsy. 1 Even with negative TTG, biopsy may still be indicated given the high prevalence in this population. 1

Treatment Approach

Initiate oral iron supplementation immediately with ferrous sulfate once daily (100-200 mg elemental iron), as this is first-line therapy and can resolve pruritus within days to weeks. 2, 3

Iron Replacement Protocol

• Administer once daily rather than multiple times per day to improve tolerance 2
• Add vitamin C to enhance absorption 2
• Expect hemoglobin to rise by approximately 2 g/dL after 3-4 weeks 2
• Continue treatment until anemia is corrected AND iron stores are replenished 2
• Consider intravenous iron if: 2, 4
  • Patient cannot tolerate oral iron
  • Inadequate response to oral therapy
  • Conditions affecting iron absorption (such as celiac disease with severe villous atrophy) 1
  • Severe symptoms requiring rapid correction

If Celiac Disease is Confirmed

Many patients with mild iron deficiency and celiac disease may respond to a gluten-free diet alone, but this can be slow. 1 Oral iron supplementation along with a gluten-free diet is indicated when symptoms are present. 1 Patients with more severe villous atrophy are less likely to respond to oral iron and may require intravenous iron. 1

Alternative Differential Diagnoses to Consider

While iron deficiency is the leading diagnosis, the British Association of Dermatologists guidelines outline other causes of generalized pruritus without rash that should be considered: 1

Hematological Disorders (2% of cases)

• Polycythemia vera - characterized by aquagenic pruritus (intense itching after water contact) 1
• Hodgkin lymphoma - presents with nocturnal itching, weight loss, fevers, and night sweats 1
• Iron overload/hemochromatosis - paradoxically can also cause pruritus 1

Check: Full blood count, blood film, lactate dehydrogenase, and ESR if hematological disorder is suspected. 1

Other Systemic Causes

• Hepatic disease (especially cholestasis) 1
• Renal disease/uremia 1
• Endocrine disorders 1
• Malignancy 1
• Drug reactions 1

Common Pitfalls to Avoid

• Do not rely solely on ferritin levels - they can be falsely elevated in inflammatory conditions 1
• Do not miss celiac disease - it is highly prevalent in vegetarians with iron deficiency anemia 1, 5
• Do not continue oral iron indefinitely without response - if no improvement after 3-4 weeks, investigate further or switch to IV iron 2
• Do not forget to investigate the underlying cause - even while treating the iron deficiency 3, 5
• Do not screen for celiac disease if the patient has already been avoiding gluten - this will cause false negatives 1

Follow-up Strategy

If anemia and pruritus do not resolve within 6 months, consider further investigation including: 2

• Bidirectional endoscopy (gastroscopy and colonoscopy) if not already performed 5
• Small bowel investigation (capsule endoscopy, CT or MRI enterography) if red flags present 5
• Re-evaluation for other causes of generalized pruritus 1