Can a hookworm infection explain the low neutrophil (white blood cell) count, high lymphocyte (white blood cell) count, and eosinophilia (high eosinophil count) in a patient with mild iron deficiency anemia?

Hookworm Infection Explains This Clinical Picture

Yes, hookworm infection fully explains the eosinophilia and iron deficiency anemia in this patient, and the relative lymphocytosis with low-normal neutrophils is consistent with a parasitic infection pattern. 1, 2

Understanding the Laboratory Findings

The Eosinophilia (7%)

• Eosinophilia is the hallmark hematologic finding in hookworm infection, occurring as a direct immune response to the parasitic invasion 2, 3
• The 7% eosinophil count (absolute count approximately 262 cells/μL based on total WBC of 3740) represents mild eosinophilia that is characteristic of chronic helminthic infections 3
• Hookworms trigger eosinophil production as part of the type 2 immune response against tissue-invasive parasites 2

The Iron Deficiency Anemia

• Hookworms are bloodsucking nematodes that attach to the small intestinal villi and cause chronic gastrointestinal blood loss, making them one of the leading causes of iron deficiency anemia worldwide 2, 4
• The hemoglobin of 13.3 g/dL in a 15-year-old male is at the lower limit of normal (normal range approximately 13.5-17.5 g/dL for adolescent males), and the elevated RDW of 15.6 indicates anisocytosis consistent with iron deficiency 1, 5
• Both fourth-stage larvae (L4) and adult worms feed on blood, causing intestinal capillary blood loss that directly depletes iron stores 2
• Hookworm is specifically listed as an uncommon but recognized cause of iron deficiency anemia in gastrointestinal disease guidelines 1

The Lymphocyte Predominance and Neutrophil Pattern

• The 52% lymphocytes with 40% neutrophils represents a relative lymphocytosis, which is common in chronic parasitic infections 3
• In adolescents and adults, lymphocyte percentages above 45-50% with corresponding lower neutrophil percentages can occur with chronic infections, particularly parasitic diseases 3
• The absolute neutrophil count (approximately 1496 cells/μL) is actually within normal range, not truly low—this is a relative finding due to the lymphocyte predominance 3
• The total leukocyte count of 3740 is at the lower end of normal, which can occur with chronic parasitic infections 3

Clinical Correlation

Why This Fits Hookworm Disease

• The combination of iron deficiency anemia with eosinophilia is pathognomonic for hookworm infection in patients from or with exposure to endemic areas 4, 3, 6
• The several-month duration fits the natural history of chronic hookworm infection, which causes progressive iron depletion 2, 4
• Hookworm disease typically presents with hypochromic microcytic anemia (though MCV data not provided here, the elevated RDW suggests this) and eosinophilia 4, 7

Geographic and Epidemiologic Context

• Hookworm (Necator americanus and Ancylostoma duodenale) is endemic in tropical and subtropical regions of the Americas, Africa, southern Asia, and Polynesia 2
• Family-wide infection is common due to shared environmental exposure to contaminated soil 2, 3

Diagnostic Confirmation Needed

• Stool examination for ova and parasites should be performed, though hookworm can be missed on single stool examinations 6
• Multiple stool samples (typically 3 specimens) increase diagnostic sensitivity 6
• In cases where stool examination is negative but clinical suspicion remains high, upper endoscopy with duodenal examination can directly visualize and retrieve adult worms 6

Treatment Implications

• Standard therapy is albendazole or mebendazole for parasite eradication 2, 4, 7
• Iron supplementation is essential to replenish depleted iron stores after deworming 4, 7
• All family members should be evaluated and treated given the suspected household exposure 3

Important Caveat

• While hookworm explains the eosinophilia and iron deficiency, confirm the diagnosis with stool studies before attributing all findings to parasitic infection 6
• The mild anemia warrants investigation per guidelines, though in the context of confirmed hookworm with family exposure, extensive gastrointestinal evaluation for other causes may not be immediately necessary 1