Teaching Case

A 27-year-male known case of haemophilia (Type A) presented for MRI swelling left knee. On examination, a large swelling was present with a history of slow enlargement for 5-year. Lab results show Hb 4.0 gm/dl ( microcytic hypochromic anaemia) with raised PT and APTT (14 and 99.7 sec), respectively.

Radiograph left knee (Fig 1a,b), frontal and lateral projections showed a large, soft tissue swelling with scalloping, erosion and permeative pattern of destructions involving mid and distal femur. Gross undulating periosteal reaction, cortical thickening and bony trabeculations are seen crossing the lesion.

On MRI, a sizeable lobulated well-defined expansile lesion was seen with diffuse heterogeneous mixed signal intensity and well-defined hypo-intense capsule in T1WI axial and coronal images (figure 2a,2b).Eccentrically placed distal femur with hypo-intense trabeculation seen extending into the lesion on axial images.

T2WI(Fat sat) images show similar intensity signal lesions with profound discrete areas of hypointensities (Fig 3a,3b). Figure 3b sagittal section shows anterior displacement of the distal femur with profound cortical destruction and osseous interruptions. Patella was seen displaced Antero-inferiorly (not shown).

T2* GRE axial image (fig 4) shows widespread areas of GRE blooming within the lesion and into the peripheral rim. 

Hemophilic pseudotumour is a rare complication of haemophilia developing in about 1-2% of Hemophilic patients, exclusively in males [1,2]. A Pseudotumour is an encapsulated, slowly expanding, chronic hematoma involving either a muscle/soft tissue or a bone that contains blood products from different ages of evolution. The capsule comprises of thick fibrous seta with hemosiderin-laden macrophages[3]. Soft tissue pseudotumours are most common in the thigh, gluteal region and iliopsoas muscle.Periosseous/intraosseous lesions cause widespread bony destructions with pathological fractures. The pressure effect due to the slow expansion of hematoma may cause pain, skin necrosis, compartment syndrome, joint contractures and compression of the neurovascular bundle [4,5]. Femur, pelvis, tibia and hand bones are most commonly involved [6]. Soft tissue and bony lesions may coexist in some cases.

Findings in plain radiography vary widely depending on the extent, location, cortical or medullary bone destruction and often atypical. Soft tissue masses with widespread destruction mimic neoplasms and other infectious conditions. Findings of Hemophilic joint arthropathy in an adjacent joint may be a clue. Osseous lesions are often expansile with lytic nature, Osseous trabeculae are seen traversing the lesion with or without periosteal reaction. Deformity and pathological fracture often result. CT helps evaluating bony trabeculae, cortical changes and periosteal reaction. MR shows clear outline, extension/infiltration of muscle/soft tissue plane, neurovascular bundle involvement and extent of bony damage.MR is valuable, mainly depicting intralesional blood products in different ages of evolution. The characteristic fibrous nature of capsules with T1 and T2 hypo intensity is suggestive of diagnosis [7]. By allowing detection of acute haemorrhage, MR influences the management regarding the need for factor replacement.

Ideal treatment may differ on a case-to-case basis. Pseudo-tumours from recent haemorrhages require clotting factor replacement and immobilisation, while surgical management is reserved for patients not responding to conservative treatment [8]. Preoperative arterial embolisation helps control intraoperative bleeding in cases of giant pseudotumour. CT/MRI play a fundamental role in monitoring and evolution of soft tissue/muscle hematoma. Radiation therapy may be helpful where surgery is contraindicated [9]. Radiation therapy in recommended doses is small, 2 Gy or less, until a total amount of 6-23.5 Gy is reached when surgery is contraindicated [10].

Take home Message

Characteristics findings of blood products on different ages of evolution with positive patient history plays a crucial role in suggesting the diagnosis as histological diagnosis in these cases not recommended due to profound risk of bleeding (fistula formation and infection).

Written informed patient consent for publication has been obtained.