CASE 15459 Published on 31.01.2018

A paediatric case of primary synovial chondromatosis

Section

Paediatric radiology

Case Type

Clinical Cases

Authors

Romano Nicola, Sertorio Fiammetta, Schiaffino Simone, Magnano Gian Michele

Genova, Italy;
Email:fiammetta.sertorio@gmail.com
Patient

4 years, male

Categories
Area of Interest Musculoskeletal bone ; Imaging Technique MR, CT
Clinical History
A four-year-old patient presented with a large mass at the medial side of the right ankle joint without pain or restriction of motion.
Imaging Findings
X-ray (Fig. 1) revealed multiple radiopaque loose bodies adjacent to the medial malleolus, projected on the medial and posterior side of the talus, associated with soft tissue swelling. MRI (Fig. 2) confirmed the presence of the loose bodies and increased thickness of the synovium. Abnormal signal intensity of bone marrow was not detected and DWI sequences (B0-B1000) showed no restriction of diffusion. The calcific loose bodies were better characterised with CT (Fig. 3), which proved useful to confirm ossification with the typical central fat attenuation; no bone erosions were detected. 3D CT was performed to guide biopsy.
Discussion
Primary synovial chondromatosis (SC) or synovial osteochondromatosis (SOC) is a rare benign neoplastic process with hyaline cartilage nodules in the subsynovial tissue of a joint, tendon sheath, or bursa. It typically occurs in the 3rd to 5th decade of life with incidence peak in the 5th decade. Men are most commonly afflicted.
Occurrence rate in adults is 1:100, 000 among the general population and it is even rarer in children. [1, 2] Frequently, SC is a mono-articular condition that involves the larger joints, including knee (50-65%), hip, elbow, temporomandibular joint and rarely affects shoulder, wrist and ankle.
Clinical symptoms are unspecific and include pain, joint swelling and restriction of the motion range. Physical examination can reveal articular crepitus, palpable nodules or a local mass and muscle atrophy. [3, 4, 5, 6]
In paediatric patients, SC can mimic monoarticular juvenile idiopathic arthritis [2, 3]. X-ray is frequently the first examination and can be useful to demonstrate calcified loose bodies. Radiopaque bodies are visible in 70-95% of cases and are usually smaller than 2-3 cm [3]. These calcifications are usually innumerable and similar in shape and show a typical “target” appearance: a central focus with a single peripheral rim of calcification. [3]
CT is the best imaging technique to detect and characterise calcifications; it can identify the multiple nodules, the characteristic ring-and-arc or punctate mineralisation and it can evaluate extrinsic bone erosion. [3]
Ultrasonography shows numerous echogenic bodies within the surrounding fluid and the thickened synovium. When the process of mineralisation is extensive, US can be useless. Power Doppler examination reveals an avascular process. [2, 3]
Three typical MRI patterns are described by Kramer [7], depending on the degree of calcifications. The most frequent pattern shows intraarticular isointensity to that of muscle on T1w images and high signal on T2w images and focal areas of low intensity in all sequences. The second pattern is similar but with no focal areas of low intensity. The third pattern includes high-signal-intensity foci with a peripheral rim of low signal that represents foci of enchondral ossification on radiographs or CT.
MRI is useful to detect bursal extension of intraarticular primary synovial chondromatosis and to exclude marrow invasion. [3]
Histological features with radiologic correlations are essential for a correct diagnosis.
The treatment of choice for SC is surgical resection after a symptomatic treatment with anti-inflammatory drugs in early phases. [2]
Differential Diagnosis List
Primary synovial chondromatosis
Secondary synovial chondromatosis
Pigmented villonodular synovitis (PVSN)
Vascular malformation (synovial haemangioma)
Osteochondritis dissecans
Synovial chondrosarcoma
Final Diagnosis
Primary synovial chondromatosis
Case information
URL: https://eurorad.org/case/15459
DOI: 10.1594/EURORAD/CASE.15459
ISSN: 1563-4086
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