Urinary findings in a 12-year-old child, a rare case of Follicular Cystitis.

Follicular cystitis (FC) is a chronic form of cystitis with uncertain etiology, characterized by the presence of lymphoid follicles in the bladder mucosa as a result of chronic irritation. This can be caused by various factors such as prolonged catheterization, lithiasis, recurrent urinary tract infections or neoplastic bladder pathology. Although it is a rare pathology, it is mainly seen in women over 50 years of age and manifests with nonspecific urinary symptoms such as dysuria, pollakiuria, haematuria and suprapubic pain. We describe a case of a 12-year-old boy with dysuria, haematuria and hypogastric pain. Despite the absence of a history of lithiasis or trauma, and no bacteria found in urinalysis, erythrocytes and leukocytes were found, along with reactivated and degenerated urothelial cells accompanied by heterogeneous-sized cells with a high nucleus/cytoplasm ratio. Ultrasonography showed no abnormalities, but cystoscopy revealed irregularities in the trigone of the bladder and biopsy confirmed the presence of lymphoid follicles, characteristic of FC. This case underscores the relevance of considering FC in patients with persistent bladder irritation and recurrent haematuria. Cystoscopy and histologic evaluation are crucial for an accurate diagnosis, although the role of the clinical laboratory is limited, an experienced specialist can facilitate a proper diagnosis.