A 32-year-old male presented with constipation, painful defecation, and streaks of blood in stools on and off. He also complained of abdominal discomfort, generalized weakness, and easy fatiguability for three months, along with loss of appetite and weight. There was no history of diarrhea, fever, or drug intake.
On examination, he was conscious and oriented with stable vitals. Pallor and mild icterus were present. Abdominal examination revealed mild tenderness in the left iliac fossa without organomegaly.
Initial blood investigations were consistent with Pancytopenia (Hb 6.9 g/dL, MCV 112 fL). Peripheral smear showed macrocytosis, ovalocytes, target cells, and hypersegmented neutrophils, suggestive of megaloblastic anemia. Biochemistry revealed mild indirect hyperbilirubinemia and mildly elevated transaminases. Serum vitamin B12 was 83 pg/mL and folate 1.2 ng/mL. Intrinsic factor and parietal cell antibodies were negative, ruling out pernicious anemia. Fecal Calprotectin was elevated.
CT Enterography showed diffuse smooth mucosal enhancement of small and large bowel loops, pulled up caecum and suspicious inflammatory changes in ileocaecal junction.
Upper GI endoscopy revealed erosive bulbar duodenitis and erosive gastritis, while colonoscopy demonstrated ulcerative(<15mm) terminal ileitis and pancolitis with scattered aphthoid ulcers (<3 mm) along the colon.
Histopathology from terminal ileum showed patchy severe active ileitis with ulceration and reactive lymphoid hyperplasia, while colonic biopsies showed focal mild active colitis, both negative for granulomas, dysplasia, and malignancy. Jejunal biopsy showed mild active jejunitis, and gastric biopsy revealed chronic active gastritis with mild atrophy, H. pylori negative. GeneXpert for tuberculosis and ASCA (IgA) were negative.
A Diagnosis of Crohn’s disease involving the terminal ileum and colon, presenting as vitamin B12 deficiency anemia with pancytopenia, was made.
The patient was managed with parenteral vitamin B12 injections, folic acid, PPIs, and supportive therapy, along with aminosalicylates and systemic corticosteroids after confirmation of inflammatory bowel disease. He showed significant symptomatic and hematologic improvement and was discharged in a stable condition with advice for gastroenterology follow-up.
Crohn’s disease (CD) is a chronic idiopathic inflammatory bowel disease (IBD) characterized by transmural granulomatous inflammation that can involve any segment of the gastrointestinal tract — most frequently the terminal ileum. The disease typically presents with chronic diarrhea, abdominal pain, and weight loss. However, in a subset of patients, extraintestinal or atypical presentations may precede classic symptoms.
In the present case, the index manifestation was severe macrocytic anemia with bicytopenia, with few gastrointestinal complaints. This atypical presentation delayed the suspicion of IBD until endoscopic evaluation and histopathology confirmed ileocolonic Crohn’s disease.
Vitamin B12 absorption occurs in the terminal ileum through an intrinsic factor–dependent mechanism. Involvement of this segment in Crohn’s disease leads to:
Additionally, chronic inflammation and malnutrition in Crohn’s disease may contribute to folate deficiency, compounding megaloblastic anemia.
Hematologic manifestations are common in IBD and include:
In our patient, pancytopenia with macrocytosis, low serum B12 and folate, and negative intrinsic factor/parietal cell antibodies established nutritional megaloblastic anemia secondary to Crohn’s ileitis, confirmed by histology.
Endoscopy revealed erosive gastritis, duodenitis, and ulcerative terminal ileitis with aphthoid ulcers throughout the colon—findings consistent with Crohn’s disease.
Histopathology demonstrated patchy active ileitis with ulceration and reactive lymphoid hyperplasia, but no granulomas—consistent with non-caseating Crohn’s inflammation rather than tuberculosis.
GeneXpert for MTB and ASCA (IgA) were negative, further supporting the diagnosis of Crohn’s colitis–ileitis rather than intestinal TB.
This case emphasizes the importance of considering Crohn’s disease in patients with unexplained megaloblastic or pancytopenic anemia, especially in younger individuals without nutritional or autoimmune etiology. The ileal pathology was uncovered only after B12 deficiency prompted GI evaluation — highlighting the need for a gut-directed workup in hematologic presentations.
Early recognition allows:
Dr. S. Akash Kumar MBBS DNB Resident, General Medicine Kauvery Hospital, Alwarpet, Chennai.
Dr. S. Sivaram Kannan MBBS, MD(Gen.Med), FRCP Clinical Lead & Chief Consultant Physician, General Medicine Kauvery Hospital, Alwarpet, Chennai.
Dr. S. Vadivel Kumaran MBBS, MD(Gen.Med), DM(Med.Gastro) Senior Consultant, Gastroenterology and Interventional Endoscopy Kauvery Hospital, Alwarpet, Chennai.
