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Hereditary Multiple Exostoses Presenting with Urinary Tract Obstruction Secondary to Imaging-Suspected Malignant Transformation: A Case Report

Mehdi Ghaderian Jahromi, Farima Safari, Ali Nabavi, Mohammad Bagher Shamsodini Moghadam, Hossein Afrakhteh

International Medical Case Reports Journal, 2026

Abstract

Background Hereditary multiple exostoses is a rare autosomal dominant skeletal disorder characterized by the development of multiple osteochondromas, with imaging findings suggestive of malignant transformation to chondrosarcoma occurring in a small proportion of patients. Such transformation typically presents with localized pain or deformity. Few reports describe urinary tract manifestations of pelvic osteochondromas; however, presentation with urinary obstruction secondary to imaging-suspected malignant transformation appears to be exceptionally rare. Case Presentation A 28-year-old Iranian man presented with a three-week history of dull right lower back pain and progressive urinary difficulty. No gross hematuria was reported although microscopic hematuria was detected on urinalysis. Ultrasonography demonstrated moderate right-sided hydronephrosis. Contrast-enhanced computed tomography of the abdomen and pelvis revealed multiple osteochondromatous lesions arising from the bilateral iliac and femoral bones, along with an infiltrative heterogeneous soft-tissue mass originating from the largest pelvic exostosis, were suspicious for malignant transformation to chondrosarcoma. The mass caused extrinsic compression of the right distal ureter, explaining the patient’s urinary symptoms. Based on imaging findings, a provisional diagnosis of hereditary multiple exostoses complicated by secondary chondrosarcoma was made. Histopathological confirmation was not obtained because the…

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