Case Report: Monoclonal gammopathy associated enteropathy: a potential MGCS related phenotype with response to plasma cell directed therapy.

BACKGROUND: Chronic inflammatory diarrhea with preserved mucosal architecture remains diagnostically challenging when inflammatory bowel disease, autoimmune enteropathy, and infection are excluded. The potential contribution of monoclonal gammopathy in such cases remains poorly defined. CASE PRESENTATION: We report two patients with long-standing, treatment-refractory chronic diarrhea who underwent comprehensive clinical, histopathologic, and hematologic evaluation. Both demonstrated a consistent intestinal pattern characterized by preserved mucosal architecture, absence of crypt distortion or epithelial apoptosis, diffuse polyclonal plasma cell-rich inflammation, and negative Congo red staining. Each patient was found to have a circulating monoclonal immunoglobulin. Conventional therapies were ineffective. Initiation of plasma cell-directed therapy resulted in rapid and sustained resolution of diarrhea, accompanied by marked reduction or disappearance of the monoclonal immunoglobulin. CONCLUSION: These findings suggest that circulating monoclonal immunoglobulins may contribute to a previously underrecognized form of inflammatory enteropathy within the spectrum of monoclonal gammopathy-associated disorders. Further studies are required to determine whether this represents a distinct clinical entity.