Intramuscular cavernous hemangioma with juxta-articular swelling

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Figure. A 19-year-old man presented with painless swelling of his left knee that was prominent on standing but that resolved completely when supine.

The patient reported experiencing recurrent, painless swelling of his left knee since he was 8 years old (Fig. 1). There was no preceding trauma. He had pain and swelling once or twice a year that lasted about a month. None of his symptoms suggested local or systemic inflammation. The patient had received a diagnosis of presumed juvenile arthritis and had taken NSAIDs on and off for years. Aspiration of the swelling, done elsewhere, yielded only blood. Results of a preliminary screening for coagulation disorders (platelet count, bleeding time, clotting time, prothrombin time and activated partial thromboplastin time) were negative.

Fig. 1: Left knee with painless swelling on standing.

The patient's skin over his left knee was normal, and there was no limitation of movement. MRI scans showed a soft-tissue mass below the anterior thigh muscles (images available online at www.cmaj.ca/cgi/content/full/175/9/1059/DC1), which suggested a partially sclerosed hemangioma with no communication with the joint cavity.

Hemangiomas are uncommon as a cause of recurrent joint swelling and, as in the case of our patient, are frequently misdiagnosed, which can lead to diagnostic delays. The swelling classically increases on standing and reduces on lying down because of emptying of the hemangioma. Hemangiomas are considered hamartomatous malformations or benign neoplasms of normal vascular tissues. Capillary hemangiomas consist of capillaries communicating freely with the systemic circulation, whereas cavernous hemangiomas are made up of dilated endothelial cavities with minimal connection to systemic circulation. Cavernous hemangiomas are more likely than arteriovenous malformations to present as juxta-articular swelling.¹ They usually present as an asymptomatic mass and cause pain and restriction of movement if they involve the deep fascia and muscles. Intramuscular hemangiomas make up 0.8% of all hemangiomas and are usually seen in the thighs. The most important differential diagnosis is hemarthrosis and pigmented villonodular synovitis, conditions easily distinguished with the use of MRI.

Intramuscular hemangiomas normally fibrose and resolve over time without any intervention. However, percutaneous sclerotherapy, radiotherapy, surgery, embolization and freezing have been used for treatment in persistent cases.

Nigil Haroon Amita Aggarwal Department of Immunology Sanjay Gandhi Postgraduate Institute of Medical Sciences Lucknow, India