Treatment-Resistant Immunoproliferative Small Intestinal Disease (IPSID) Leading to Lymphoma.

Immunoproliferative small intestinal disease (IPSID) is a distinct variant of mucosa-associated lymphoid tissue (MALT) lymphoma, often linked to chronic infection. Characterized as an extra-nodal marginal zone B-cell lymphoma, IPSID predominantly affects the proximal small intestine. It features lymphoplasmacytic infiltration and deposition of monotypic α-heavy chains in the lamina propria, leading to blunted intestinal villi, malabsorption, and protein-losing enteropathy. IPSID's clinical spectrum ranges from lymphoid infiltration to malignant diffuse large B-cell lymphoma. Similar to MALT lymphoma, early-stage IPSID can be resolved with antibiotic therapy. This case study documents a 50-year-old Nigerian woman presenting with recurrent watery diarrhea, abdominal pain, and weight loss, unresponsive to antibiotics. A 50-year-old female immigrant from Nigeria presented with recurrent watery diarrhea, abdominal pain, and significant weight loss, all refractory to antibiotic treatment. Initial diagnostic investigations revealed a positive stool antigen, mesenteric lymphadenopathy on CT and gallium scans, and diffuse mucosal lymphoplasmacytic infiltration with villi flattening on small bowel biopsies. An octreotide scan identified a reactive mesenteric lymph node, confirmed by surgical biopsy as reactive lymphadenitis. The patient was diagnosed with IPSID and commenced antibiotic therapy, which initially resolved her symptoms. However, she experienced frequent recurrences requiring multiple hospitalizations and repeated courses of intravenous antibiotics. Eventually, the disease progressed to lymphoma, necessitating chemotherapy initiation. This case underscores the diagnostic complexities of IPSID, particularly in distinguishing it from other causes of mesenteric lymphadenopathy. It also highlights the challenges in preventing disease progression from a benign to a malignant state despite appropriate antibiotic treatment. Given IPSID's prevalence in endemic regions, it should be considered in differential diagnoses for similar presentations. Continuous monitoring is crucial to evaluate therapeutic response and mitigate the risk of progression to lymphoma. IPSID presents a significant diagnostic and therapeutic challenge. This case exemplifies the necessity for heightened clinical awareness, especially in patients from endemic regions, and the importance of rigorous monitoring to prevent malignant transformation. Further research is warranted to elucidate the mechanisms behind IPSID progression in certain patients despite repeated antibiotic interventions.