Identification of a rare case of intra-articular osteochondroma manifesting as three loose bodies in a patient with hereditary multiple osteochondromas: A case report

摘要

Hereditary multiple osteochondromas (HMO) is an autosomal dominant hone disorder characterised by the presence of multiple benign cartilage-capped tumours. Exostosin-1 (EXT1) and EXT2 are the major morbigenous genes associated with HMO, mutations in which are responsible for 90% of all HMO cases. In patients with HMO, osteochondromas arise adjacent to the metaphysis and typically remain in the metaphyseal region of the long bones. Therefore, it is rare for osteochondromas to be identified intra-articularly, although they may manifest as loose bodies. The present study describes a rare case of HMO manifesting as limited flexing range in the right knee joint of a 27-year-old male patient. Computed tomography and magnetic resonance imaging (MRI) revealed three intra-articular osteochondromas located in the intercondylar fossa of the patient's right knee. The intra-articular ostcochondromas and protuberant extra-articular osteochondromas around the right knee were.resected, resulting in improved right knee function and no postoperative recurrence. Pathological nalysis revealed that the intra-articular ostcochondromas had a thinner cartilage cap layer than the extra-articular osteochondromas. In addition, genetic analysis of the patient and the patient's mother was conducted. From this, it was determined that a nonsense mutation, c..115G>T (p.E39X) in exon 1 of the EXT.I. gene, was the cause of HMO in this case. Thus, it is proposed that osteochondromas with a pedicle within the knee, may tear and become loose intra-articular bodies, resulting in limited joint function and thereby contributing to the progression of HMO.