Iron deficiency anemia (IDA)

A 35 year old woman presents to her primary care physician with a history of fatigue and generalized weakness for 6 months. She reports shortness of breath on exertion and has developed pica, specifically craving and eating ice. She follows a vegetarian diet. She also reports chronic rectal bleeding, noticing bright red blood on the toilet paper and on the surface of the stool. She denies pain during defecation but has anal itching and discomfort. She has a history of chronic constipation with straining. On examination, there is pallor of the skin and conjunctiva. No lymphadenopathy or hepatosplenomegaly is present. On per rectal examination, external hemorrhoids are noted. Laboratory studies show low hemoglobin with low MCV. Iron studies reveal low ferritin, low serum iron, high TIBC, and low transferrin saturation. Diagnosis?

Diagnosis is Iron deficiency anemia, most likely secondary to chronic blood loss, with hemorrhoids as a probable source; however, further evaluation for gastrointestinal bleeding is required.

1. Definition

Iron deficiency anemia is a microcytic hypochromic anemia caused by insufficient iron availability for hemoglobin synthesis.

2. Etiology

1. Chronic blood loss
• Gastrointestinal bleeding including hemorrhoids, but occult malignancy must be excluded
• Menstrual blood loss
2. Decreased iron intake
• Vegetarian diet
3. Increased requirements
• Pregnancy, growth
4. Malabsorption
• Celiac disease, post gastrectomy

3. Pathophysiology

1. Depletion of iron stores
2. Reduced heme synthesis
3. Decreased hemoglobin production
4. Formation of microcytic hypochromic red blood cells
5. Iron is primarily absorbed in the duodenum

4. Clinical Features

1. Fatigue and weakness
2. Dyspnea on exertion
3. Pallor
4. Pica, especially pagophagia
5. Koilonychia
6. Glossitis and angular cheilitis

Associated syndrome:

• Plummer Vinson syndrome
• Iron deficiency anemia
• Esophageal webs
• Dysphagia

5. Diagnosis

5.1 Complete Blood Count

1. Low hemoglobin
2. Low MCV <80 fL
3. Increased RDW

5.2 Iron Studies

1. Low ferritin (most specific)
2. Low serum iron
3. High TIBC
4. Low transferrin saturation

5.3 Additional Tests

1. Elevated soluble transferrin receptor
2. Increased free erythrocyte protoporphyrin
3. Mentzer index >13 suggests iron deficiency over thalassemia
4. Possible reactive thrombocytosis

6. Management

1. Identify and treat the underlying cause
• Evaluate for gastrointestinal bleeding, including endoscopic assessment if indicated
2. Iron replacement therapy
• Oral iron such as ferrous sulfate is first line
• Take with vitamin C to enhance absorption
3. Intravenous iron
• For intolerance, malabsorption, or severe deficiency
4. Monitoring response
• Reticulocytosis occurs within 5 to 7 days
• Hemoglobin improves over weeks

7. Complications

1. Severe anemia leading to cardiac strain
2. Impaired cognitive and physical performance
3. Restless leg syndrome

8. Key Clinical Insight

Microcytic anemia with low ferritin and pica in a patient with chronic rectal bleeding strongly indicates iron deficiency anemia, but gastrointestinal malignancy must be excluded in adults

9. Exam Level Pearls

1. Low ferritin is the most specific marker of iron deficiency anemia
2. Pica, especially ice craving, is a classic feature
3. High TIBC differentiates iron deficiency from anemia of chronic disease
4. Mentzer index >13 favors iron deficiency over thalassemia
5. Always evaluate chronic blood loss anemia in adults for occult gastrointestinal malignancy