Ileocaecal tuberculosis: an under-recognised cause of vitamin B 12 deficiency

Case report

A 16-year-old boy was admitted for low-grade intermittent fever for three months along with mild diffuse abdominal pain, anorexia and involuntary weight loss. On examination, the vital signs were normal. He was pale and had hyperpigmentation over the knuckles of both hands (Figure 1a). Abdominal examination revealed tenderness in the right lower quadrant and mild hepatosplenomegaly. The remainder of the examination was normal. Investigations showed a haemoglobin of 85 g/L, macro-ovalocytes on peripheral blood smear and a low serum vitamin B₁₂ level (51 pmol/L: N > 147). The white blood cells, platelets, renal functions and liver functions were within normal range. The chest radiograph was normal. An abdominal ultrasound was also unremarkable except for mild hepatosplenomegaly. A tuberculin skin test was positive. Subsequently, a contrast-enhanced computed tomography (CT) of the chest and abdomen was performed, which revealed centrilobular nodules with a tree-in-bud appearance in both lungs, abdominal lymphadenopathy, and thickening of the terminal ileal and caecal walls with a patulous appearance of the ileocaecal valve (Figure 1b). A colonoscopy showed multiple erosions over the ileocaecal valve and the terminal ileum. The patient was ultimately diagnosed as having vitamin B₁₂ deficiency due to ileocaecal tuberculosis (TB) and was treated with four drug anti-tubercular therapy and intramuscular cyanocobalamin injections (1000 µg daily for one week, then weekly for one month, and then one dose monthly). At follow-up visits, his symptoms gradually improved. OPEN IN VIEWER

Discussion

Vitamin B₁₂ deficiency in adults usually results from a pure vegetarian diet, gastrointestinal surgical resection and pernicious anaemia. ¹ As the terminal ileum is the site of vitamin B₁₂ absorption, conditions causing chronic mucosal inflammation such as inflammatory bowel disease and TB may lead to malabsorption and may eventually result in megaloblastic anaemia.

Anaemia in TB is usually due to chronic disease, iron deficiency secondary to chronic intestinal blood loss or associated malnutrition.^2,3 Vitamin B₁₂ deficiency is rarely reported despite the ileocaecal region being the commonest site for abdominal TB.^2–4 Ileocecal TB results in mucosal thickening, multiple ulcerations, strictures, adhesions or bowel narrowing. ⁴ Mural thickening of the ileocaecal region (symmetric or asymmetric) or a patulous ileocaecal valve on the CT scan are common as well as characteristic signs of the disease.^4,5

For clinicians who treat TB, a high index of suspicion for vitamin B₁₂ deficiency is warranted, given the prevalence of anaemia with the disease. Vitamin B₁₂ deficiency may result in subacute combined degeneration and neuropathy.