Thymic Lymphoid Follicular Hyperplasia in a Young Woman with Refractory Ulcerative Colitis and Thyroid Autoimmunity: A Case Report and Narrative Review

Abstract

Introduction and purpose. The thymus plays a key role in T-cell maturation and immune tolerance. Thymic abnormalities may accompany autoimmune diseases, but their significance in ulcerative colitis (UC) remains uncertain. This article describes a young woman with refractory UC, colitis-associated colorectal neoplasia, progressive thymic enlargement and thyroid autoimmunity, and discusses potential immunological links.

Materials and methods. A clinical case was analyzed alongside a narrative review of PubMed/MEDLINE literature on thymic immune tolerance, thymic hyperplasia, UC, colorectal neoplasia, thyroid autoimmunity and thymectomy. Reviews, observational studies and literature directly addressing thymic abnormalities in UC were prioritized.

Case presentation. A 25-year-old woman with a ten-year history of refractory UC underwent colectomy with end ileostomy. Histopathology revealed colorectal carcinoma arising in a tubulovillous adenoma with high-grade dysplasia and active UC. CT subsequently demonstrated progressive anterior mediastinal tissue enlarging from approximately 3 to 8 cm. Myasthenia gravis was excluded. Thyroid function was normal, but thyrotropin receptor antibodies were weakly positive. Thymectomy was performed because of lesion progression, revealing benign thymic lymphoid follicular hyperplasia. During follow-up, UC remained in remission after colectomy and antibody levels decreased.

Conclusion. The coexistence of severe UC, thyroid autoimmunity and thymic lymphoid follicular hyperplasia may reflect shared immune dysregulation but does not establish causality or prove a therapeutic effect of thymectomy. Further research is required before thymic imaging or thymectomy can be considered in routine UC management.