Crystal-Storing Histiocytosis of Gastrointestinal Tract: Report of 2 Patients and Literature Review.

Crystal-storing histiocytosis (CSH) is rare in the gastrointestinal tract, with only 24 patients documented to date in the English literature. We report 2 patients with CSH involving the stomach and colon respectively, each with unique histology and underlying disease. Patient 1 presented with difficulty swallowing and epigastric pain. Endoscopy revealed a focal area of cobblestone, granular and nodular mucosa in the body of the stomach. Biopsy showed expansion of the lamina propria by histiocytes containing eosinophilic crystalline material. The background infiltrate consisted of plasma cells and predominantly B lymphocytes. Extensive workup led to the diagnosis of CSH associated with B-cell lymphoma with plasmacytic differentiation. Patient 2 underwent colonoscopy, which identified colonic polyps composed of abundant eosinophils, histiocytes with intracellular eosinophilic crystalline material, and numerous mast cells. Molecular testing of the tissue revealed a KIT p.D816V mutation. The findings were consistent with colonic CSH with underlying systemic mastocytosis, representing the first reported patient of this specific presentation. Our report contributes to the limited literature on CSH of the gastrointestinal tract. In summary, within the gastrointestinal tract, the stomach is the most frequently affected site of CSH, typically in association with B-cell lymphoma. The colon is the next most commonly involved site and has been linked to a broader range of conditions, including both neoplastic disorders (including lymphoma, plasma cell myeloma, and mastocytosis) and nonneoplastic disorders, such as eosinophilic colitis and ulcerative colitis.