Gastrointestinal: Langerhans cell histiocytosis in an adult with anal protrusion and multiple colorectal ulcers

This is the authors' abstract. We don't add key points for this paper.

A 56-year-old woman with no significant past medical history presented with small pimple-like lesions around her perianal area for more than 3 months. The condition gradually worsened, and the patient experienced pain during defecation and reported a 3-kg weight loss. She admitted rare alcohol consumption, no smoking, and a noncontributing family history. Examination revealed that the anal lesions had developed into discrete protruding masses with distinct boundaries and a hyperemic surface (Fig. 1a). Laboratory findings showed microcytic hypochromic anemia. Endoscopy showed multiple colorectal ulcers, with a significant concentration in the sigmoid area. These ulcers ranged from 3 to 10 mm, had raised margins and clear borders, and were covered in the center by pseudomembranes (Fig. 1b). The initial diagnosis was suspected Crohn's disease. Histopathology of biopsied specimens from the anal and colorectal ulcer regions showed proliferation of cells with reniform (kidney-shaped) nuclei in both the submucosa and lamina propria, abundant eosinophilic cytoplasm, and a scattered presence of eosinophils (Fig. 1c,d). These cellular features on hematoxylin and eosin staining are suggestive of Langerhans cell histiocytosis (LCH). However, considering its morphological features and presentation in the gastrointestinal tract, differential diagnoses included indeterminate cell histiocytosis, Rosai–Dorfman disease, juvenile xanthogranuloma, histiocytic sarcoma, lymphoma, melanoma, and systemic mastocytosis. To clearly diagnose and differentiate LCH from other underlying conditions, immunohistochemical staining was performed. The cells expressed positivity for CD1a, S100, and langerin (CD207), confirming the diagnosis of LCH (Fig. 1e–g). The patient had a normal skin examination and a series of imaging procedures, including ultrasound, X-ray, computed tomography, and positron emission tomography/computed tomography, which showed no abnormality or other organ involvement. She is undergoing treatment with low-dose cytarabine for 5 days/month over a 12-month period, combined with regular monitoring and evaluations. Currently, the initial treatment with chemotherapy has brought positive results, with the patient showing signs of reduced lesions. Langerhans cell histiocytosis is a rare and intriguing disorder that involves the proliferation of Langerhans cells. These cells are a type of dendritic cell that plays a key role in the immune response.1 Although LCH can manifest at any age, it primarily affects children. The disease can attack any organ, but in children, it often involves the bones, skin, pituitary gland, and other organs such as the liver, spleen, hematopoietic system, and lungs.1, 2 Gastrointestinal involvement in LCH is particularly rare, accounting for approximately 2–4% of all LCH cases. Most of these gastrointestinal manifestations are diagnosed in children under 1 year of age.3 In adults, the occurrence of LCH in the gastrointestinal tract is even rarer. When it does present, it usually presents as solitary polyps. Ulcerative manifestations, especially multiple ulcers or perianal lesions, are extremely rare. Globally, only a few cases of such manifestations have been reported.1, 3 LCH has been classified into four major syndromes, including Letterer–Siwe disease, Hand–Schüller–Christian disease, eosinophilic granulomatosis, and congenital self-healing reticulohistiocytosis (also known as Hashimoto–Pritzker disease). Due to the rare nature of LCH and an incomplete understanding of its pathogenesis, treatment and chemotherapy regimens in adults are not standardized.1-3