Elusive cause of iron deficiency anaemia

Introduction

A 58-year-old woman presented to our clinic with the diagnostic and management issue of severe symptomatic iron deficiency anaemia. She described generalised abdominal discomfort but no overt evidence of gastrointestinal (GI) bleeding, loss of weight, nausea, vomiting or diarrhoea. She had no significant medical history or any regular medications. She was an avid exerciser and had walked the Kokoda Trail in Papua New Guinea 12 months prior. Her biochemistry revealed a haemoglobin of 92 g/L with a mean corpuscular volume (MCV) of 65 fL and an undetectable ferritin (<6 µg/L). Her transferrin saturation was 4%. Her eosinophil count was mildly elevated at 1.0×10⁹/L. Liver and renal function tests were within normal limits. Her coeliac serology was negative. She proceeded to have a normal gastroscopy. Her colonoscopy identified small internal haemorrhoids but no cause for her iron deficiency anaemia. She then proceeded to have a capsule endoscopy (figures 1 and 2 and online supplemental video).

Figure 1.

Capsule endoscopy view of the proximal small intestine.

Figure 2.

Capsule endoscopy view of the proximal small intestine.

Question

What is the diagnosis?

Answer

Capsule endoscopy revealed multifocal aphthous ulceration and bleeding. Live blood-filled worms were actively feeding from the mucosa in the proximal small intestine. These were morphologically consistent with hookworm. The patient was managed with an iron infusion and mebendazole. At 4 months follow-up her symptoms had resolved. Repeat blood tests revealed a normal haemoglobin (127 g/L; MCV 83) and a normal ferritin of 51 µg/L (transferrin saturation 26%). A follow-up stool test for ova, cysts and parasites was negative.

Often forgotten, hookworm infections (Necator americanus and Ancylostoma duodenale) are one of the most common worldwide causes of iron deficiency, although relatively uncommon in the Western world.¹ They are transmitted via contaminated soil and mostly localise to the small intestine.² The nematode parasite feeds on the hosts blood by attaching to intestinal mucosa, tearing into mucosal capillaries and releasing anticoagulant peptides allowing for effective ingestion of blood (see figures 1 and 2 and online supplemental video 1).³ Prolonged infection results in symptomatic iron deficiency anaemia. Diagnosis by stool examination is insensitive.⁴ In our patient, the peripheral eosinophilia was a clue to the presence of a parasitic infection, although this is often only mildly elevated.² This is an elusive cause for iron deficiency anaemia, yet easily curable and thus should remain a differential when the source of GI bleeding is obscure.

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