Haemophilic pseudotumour is a rare complication of haemophilia consisting of a progressive cystic swelling of muscle and/or bone, occurring in less than 2% of haemophiliacs.
It is reported in 1-2% of haemophiliacs patients.
Most develop in the muscles of the pelvis and lower extremity, where the large muscles have an abundant blood supply, or in bone following intraosseous bleeding.
Ultrasonography, CT and MRI have significant roles in detecting pseudotumours, especially when they are in the pelvis.
X-ray is useful in diagnosing intraosseous pseudotumours. They appear as well-defined, unilocular or multiloculated, lytic, expansile lesions of variable size. It can involve metaphysis, diaphysis and epiphysis of long bones.
Other findings include endosteal scalloping, perilesional sclerosis, cortical thinning or thickening, trabeculations and septations. Pathological fractures can also be present.
In the acute and subacute stages, sonography shows a central anechoic area with increased echoes behind the lesion, caused by fluid in the pseudotumour. A distinct plane separates the mass from the surrounding muscles.
CT shows the thick wall more consistently than does ultrasonography. Multiple irregular echoes represent solid material that cannot be documented on CT. Differential diagnosis from abscess may be difficult.
CT is useful for detecting both the extent of soft-tissue masses and the involvement of bone. Pseudotumours contain coagulated blood and are surrounded by a thick wall.
Contrast-enhanced CT is useful for determining the thickness of the wall. In the acute stage, the centre of the pseudotumour is hypodense on CT, but the periphery is isodense and indistinguishable from surrounding muscle.
The hypointense rim of a pseudotumor on both T1 and T2-weighted images consists of fibrous tissue that contains haemosiderin.
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