Can hookworm infection occur with elevated Mean Corpuscular Hemoglobin (MCH)?

Hookworm Infection Can Occur with Elevated MCH

Hookworm infection can occur with elevated Mean Corpuscular Hemoglobin (MCH) despite typically causing microcytic hypochromic anemia, as the hematological profile depends on the stage of infection, severity, and concurrent conditions. 1

Pathophysiology and Hematological Effects

Hookworm infection (primarily Necator americanus and Ancylostoma duodenale) typically causes iron deficiency anemia through chronic intestinal blood loss. The classic hematological presentation includes:

• Decreased hemoglobin
• Microcytic (low MCV) and hypochromic (low MCH) red blood cells
• Iron deficiency parameters (low ferritin, low serum iron, elevated TIBC)

However, several scenarios can lead to elevated MCH in the presence of hookworm infection:

1. Early infection stage: Before significant iron depletion occurs, hematological parameters may remain normal or even elevated due to compensatory mechanisms

2. Mixed nutritional deficiencies: Concurrent B12 or folate deficiency (common in malnourished populations) can cause macrocytosis, offsetting the microcytosis of iron deficiency

3. Hemolysis: Hookworm-induced inflammation can occasionally trigger hemolysis, leading to elevated MCH

4. Pre-existing macrocytosis: Patients with baseline macrocytosis (from alcohol use, liver disease, medications) may maintain elevated MCH despite developing hookworm-related iron deficiency

Diagnostic Approach

When encountering elevated MCH with suspected hookworm infection:

1. Stool examination: Concentrated stool microscopy remains the gold standard for diagnosis. At least three stool samples should be examined due to intermittent parasite shedding 1, 2

2. Specialized techniques:

   • Baermann technique and agar plate culture specifically for hookworm detection
   • Serology testing (detects antibodies 4-8 weeks after infection)
   • Nucleic Acid Amplification Tests (NAAT) when conventional methods fail 2

3. Complete blood count interpretation:

   • Evaluate other RBC indices (MCV, MCHC, RDW)
   • Look for dimorphic anemia pattern (mixed population of microcytic and macrocytic cells)
   • Check reticulocyte count to assess for hemolysis

4. Additional testing:

   • Iron studies (ferritin, serum iron, TIBC)
   • B12 and folate levels
   • Peripheral blood smear

Clinical Presentation

Hookworm infection presents with various symptoms:

• Respiratory: Wheeze, dry cough (Löffler's syndrome) 1
• Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain 1
• Cutaneous: Urticarial rash 1
• Systemic: Fever (during Löffler's syndrome), anemia (particularly in children) 1
• Severe cases: Overt gastrointestinal bleeding 3

Treatment

The World Health Organization recommends:

• First-line: Albendazole 400 mg as a single dose 2
• Alternative regimen: Albendazole 400 mg daily for 3 days for heavy infections 2
• Alternative agent: Mebendazole 100 mg twice daily for 3 days 2

Important Considerations

• Concurrent treatment: Address any coexisting nutritional deficiencies (iron, B12, folate)
• Follow-up: Clinical follow-up in 2-4 weeks with repeat stool examination to confirm eradication 2
• Prevention: Proper sanitation, wearing shoes, and improved hygiene practices 2

Pitfalls to Avoid

1. Overlooking hookworm in non-endemic areas: Consider hookworm in travelers returning from endemic regions, even with atypical hematological profiles

2. Focusing solely on MCH: Evaluate the complete hematological picture rather than individual parameters in isolation

3. Inadequate stool sampling: A single stool sample has limited sensitivity; multiple samples increase diagnostic yield

4. Missing concurrent infections: Hookworm often coexists with other parasitic infections that may influence hematological parameters

5. Ignoring the possibility of overt bleeding: Hookworm can occasionally cause significant gastrointestinal bleeding requiring urgent intervention 3

In conclusion, while hookworm typically causes microcytic hypochromic anemia with decreased MCH, various factors can lead to elevated MCH in infected individuals. A comprehensive diagnostic approach is essential for accurate diagnosis and appropriate management.