Spot Diagnosis - Enlarged Joint

Its habitus of Noonan syndrome.

 

Yes, U r right. But, what's the joint condition called ? and it's not specific for Noonan's.

 

Hint:

1) The histology slide shows - intra and extecellular hemosidderin

2) This is a benign lesion, with a high rate of recurrence

3) Radiation therapy helps

 

Another Hint - the arthroscopy img. is showing numerous villous structures within the joint cavity

 

Thanks for the hints neo-star. This is pigmented villonodular synovitis. It was the arthroscopy that confirmed it for me - great image!

 

Noonan syndrome

 

Ans: Pigmented Villonodular synovitis

Credit to Dr. kangourou for solving the challenge.

Discussion
Hillary Warren Garner, MD, Ӣ Cedric J. Ortiguera, MD, Ӣ Raouf E. Nakhleh, MD
RadioGraphics 2008; 28:1519”“1523 ”¢ Published online 10.1148/rg.285075190


PVNS is a member of a family of benign proliferative lesions of the synovium of the joint, bursa, and tendon sheath that are usually divided according to the site of origin (intraarticular or extraarticular) and pattern of growth (localized or diffuse) (1). The term pigmented villonodular synovitis is generally used when diffuse intraarticular involvement is present (2,3).

Although trauma, inflammation, neoplasia, and disorders of lipid metabolism have been implicated as causative factors of PVNS (4”“7), the etiology of this disease remains unclear. Recent cytogenetic studies, however, provide increasing evidence of a neoplastic origin (7).

PVNS is usually a monoarticular process of the large joints, affecting the knee in 80% of cases (4,5). It can also involve, in order of decreasing frequency, the hip, ankle, shoulder, and elbow (3”“5,8).

Although this disease can manifest at any age, it typically affects adults 20”“50 years of age, with equal frequency in men and women (3”“6,9).

Patients frequently complain of slowly progressive pain, swelling, and decreased range of motion (4”“7). A history of recurrent, bloody joint effusion is also a classic clinical finding.

PVNS in the knee typically manifests as a non-specific joint effusion on radiographs, although occasionally the fluid may appear dense, a finding suggestive of hemorrhagic effusion. Bone erosions can also be seen; these occur most frequently in the hip (more than 90% of cases) and shoulder (more than 70% of cases) (5) and may be due to a relatively small, more confined joint space
and secondary increased pressure in these joints.
Accordingly, bone erosions are less common in the more capacious knee joint (3”“5) and are seen in approximately 25% of cases (5). Although traditionally the osseous erosions are thought to be the result of pressure erosion, their exact pathogenesis remains unclear. Recent studies of ultrastructure have suggested that proteolytic enzymes expressed by the giant cells within the lesion may influence these osseous changes (7). These erosions demonstrate thin sclerotic margins and usually involve both sides of the joint.

Joint space narrowing and hypertrophic spurring, which are common in osteoarthritis, are not features of PVNS, even late in the disease process (4,7). Calcification within PVNS has been noted on radiographs (10), but it is quite unusual and should suggest an alternative diagnosis.
On arthrographic images, the nodular synovial thickening of PVNS can appear as filling defects within the joint, findings similar to those seen with synovial osteochondromatosis or rheumatoid arthritis (rice bodies) (2,4). However, these alternate diagnoses are usually readily distinguishable with other imaging modalities.
MR imaging is the preferred modality for diagnosing PVNS because of its very specific imaging features, which help to distinguish PVNS from other synovial processes. Images typically show a synovial-based mass that affects most or all of the joint and that displays low signal intensity on T1- and T2-weighted pulse sequences. Magnetic susceptibility artifact (blooming) within the affected joint space on GRE images is also characteristic. This artifact is related to the local magnetic field that is created by iron present in hemoglobin, which causes spinning nuclei to dephase and a subsequent signal void, or blooming (11). PVNS can also contain areas of variable signal intensity, with foci of brighter T1 and T2 signals that indicate relatively low concentrations of hemosiderin.
Ultimately, the signal intensity characteristics displayed by PVNS reflect the histologic nature of the lesion (3,5”“9,12). These characteristics directly correspond to the macroscopic and microscopic features of the disease, which are described as brownish red or tan projections of synovium that are composed of fibrous stroma with multinucleated giant cells, xanthomatous cells, and intra- and extracellular hemosiderin (3”“5).
Although the degree of enhancement in PVNS can vary, marked enhancement of the synovium is common due to the hypervascular nature of the disease (3,7,8).

The major conditions in the differential diagnosis of PVNS include amyloid arthropathy, hemophilia-related arthropathy, and synovial chondromatosis.
Although amyloid arthropathy typically has low signal intensity on both T1- and T2-weighted images, it does not demonstrate the blooming artifact that is seen in PVNS. The multifocal involvement seen in secondary amyloid arthropathy should also help to distinguish it from PVNS.
Hemosiderin can be seen in hemophilia related arthritis; however, the osseous deformity seen in hemophilia is not a feature of PVNS.
Synovial chondromatosis can demonstrate a spectrum of imaging features. Most frequently, it shows multiple mineralized intraarticular bodies, which are readily identifiable on radiographs. When they are nonmineralized, the cartilaginous nature of the loose intraarticular bodies is usually recognizable on MR images.

Optimal treatment of PVNS requires a complete synovectomy, which can be difficult in capacious joints such as the knee and hip where there are multiple recesses and communicating bursae. Recurrence rates are generally between 30% and 50%, although rates between 10% and 56% have been reported (7); location of disease and history of partial resection are the most important
confounding factors (1,7). Recurrent disease can appear within months, but it typically doesn’t appear until years after treatment. Although arthroscopic synovectomy has a shorter initial recovery period, open synovectomy techniques may yield a better long-term outcome, particularly in recurrent cases (7).
External beam and intraarticular radiation therapy with a beta emitter such as yttrium have also been useful, but they are usually reserved for patients with recalcitrant disease because of their potential for producing undesirable side effects, such as transformation into malignant PVNS (4,7,13).

Patients with PVNS-related joint destruction usually undergo synovectomy followed by arthroplasty or arthrodesis (4,7).

Although PVNS is a rare synovial disorder, the features of this disease on MR images are unique and facilitate differentiating it from other synovial proliferative processes. The characteristic blooming seen on GRE images and the low T1 and T2 signal intensity ultimately reflect the histologic features of the lesion.

References
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