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Today we celebrate World Rare Diseases Day, and we bring you a strange and rare disease that affects 1.8 per million.
It's called Pigmented villonodular synovitis (PVNS) or Tenosynovial giant cell tumor (TGCT) and is a rare disease that can affect any joint, tendon sheath or bursa. The name villonodular comes from the villous or nodular hyperplasia of the synovium.
This type of lesion belongs to the tenosynovial giant cell tumor.
Let's start from the beginning!
Synovium is the soft tissue lining the spaces of diarthrodial joints, tendon sheaths and bursae.
Synovium is vascularized and responsible for the transport of nutrients, debris, immune modulations, and joint inflammation. Being also responsible for the production of components essential for the synovial fluid (lubricate the cartilage).
What causes this abnormality?
The exact motif is still not completely understood but inflammation plays a key role.
It can be caused by an overexpression of CSF1 gene that leads to clusters of aberrant cells creating soft tissue hyperplasia.
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TGCT is an aggressive neoplastic synovial disease once it erodes the bone and destroys the joint, nevertheless, it is benign in other words, it is not cancerous.
The condition is extremely painful and hard to diagnose mainly because the symptoms are vague:
Excruciating pain after certain movements;
Joint lock (loss of mobility);
Swelling that goes away;
Spasms of the surrounding muscles
People with this condition lose quality of life once they can do things they once could. TGCT affects mainly the knee 70%, the hip 15% and the ankle, shoulder, and elbow.
"(Left) This MRI of an elbow shows a tumor caused by PVNS. (Right) In this MRI of the same elbow, an area where the tumor has eaten through the bone is visible."
It can be distinguished between:
Localized
When the tumor involves the tendons that support the joint or occurs in just one area of the joint. Responds well to treatment.
Diffuse
When the condition is more widespread and involves an entire joint. The most aggressive and difficult form to treat.
Treatments:
Surgical Procedures: Arthroscopic, open surgery or joint replacement
Radiation: intra-articular radiation
Drug Therapy: targeting CSF-1R
Localized rarely recurs after surgery. The recurrence rate for diffuse can be as high as 30%
Team Let's Biologue!
References
Synovium & Synovial Fluid. (2021). Physiopedia. https://www.physio-pedia.com/Synovium_%26_Synovial_Fluid
Translocation and Expression of CSF1 in Pigmented Villonodular Synovitis, Tenosynovial Giant Cell Tumor, Rheumatoid Arthritis and Other Reactive Synovitides. The American Journal of Surgical Pathology, 31(6), 970–976
Steinmetz, S., Rougemont, A., & Peter, R. (2016). Pigmented villonodular synovitis of the hip. EFORT Open Reviews, 1(6), 260–266. https://doi.org/10.1302/2058-5241.1.000021
Gitelis S;Heligman D;Morton T. (2023). The treatment of pigmented villonodular synovitis of the hip. A case report and literature review. Clinical Orthopaedics and Related Research, 239. https://pubmed.ncbi.nlm.nih.gov/2912615/
Tang, Y., M. Anthony Moody, Mi, R., Liu W, Hou, J., Feng, Y., Zhang, M., Yu, M., F, L., Song, Y., Lu, Y., Yan, Y., & Yang, R. (2021). Single-cell RNA-seq analysis reveals aberrant CSF1 expression in disease-causing synovial fibroblasts of pigmented villonodular synovitis. BioRxiv (Cold Spring Harbor Laboratory). https://doi.org/10.1101/2021.09.29.462128
Cupp, J. S., Mary Lou Miller, Montgomery, K., Nielsen, T. O., O’Connell, J. X., Huntsman, D. G., Matt, C. Blake Gilks, & West, R. B. (2007). Translocation and Expression of CSF1 in Pigmented Villonodular Synovitis, Tenosynovial Giant Cell Tumor, Rheumatoid Arthritis and Other Reactive Synovitides. The American Journal of Surgical Pathology, 31(6), 970–976. https://doi.org/10.1097/pas.0b013e31802b86f8
Sugita, S., Takenami, T., Kido, T., Aoyama, T., Hosaka, M., Segawa, K., Sugawara, T., Fujita, H., Shimizu, J., Yasutaka Murahashi, Makoto Emori, & Hasegawa, T. (2022). Diagnostic utility of CSF1 immunohistochemistry in tenosynovial giant cell tumor for differentiating from giant cell-rich tumors and tumor-like lesions of bone and soft tissue. Diagnostic Pathology, 17(1). https://doi.org/10.1186/s13000-022-01266-9
Block, A. (2020). When A Patient Has Pigmented Villonodular Synovitis. Podiatry Today, 33(5). https://www.hmpgloballearningnetwork.com/site/podiatry/when-patient-has-pigmented-villonodular-synovitis
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