Olga Amorós Carafí, Joseph O’Sullivan, Séamus Hoey, Pamela A. Kelly, Ronan A. Mullins
Background
Hemophilia A is an inherited coagulation disorder resulting from factor VIII deficiency, leading to spontaneous bleeding and hematoma formation. In humans, repeated intramuscular hemorrhage may lead to the development of hemophilic pseudotumors—chronic, encapsulated hematomas that mimic neoplasia. While musculoskeletal bleeding manifestations are recognized in dogs, soft-tissue hemophilic pseudotumors have not previously been reported. This study documents the first canine case of an intramuscular hemophilic pseudotumor, highlighting imaging features, surgical management, and long-term outcome.
Methods
An 8-month-old male Cocker Spaniel with a confirmed diagnosis of hemophilia A (factor VIII activity 3%) presented with a 3-week history of severe right pelvic limb lameness and thigh swelling. Diagnostic evaluation included pre- and postcontrast CT imaging of the caudal abdomen and pelvic limbs using a 16-slice scanner. The lesion’s characteristics, periosteal changes, and lymph node involvement were evaluated. Radiographs were obtained at presentation and 1 month postoperatively. Following plasma transfusion for factor VIII replacement, the mass was surgically excised via a craniolateral femoral approach, and samples were submitted for culture and histopathology.
Results
CT revealed a large, heterogeneous, rim-enhancing soft-tissue mass enveloping the right femoral diaphysis and adjacent muscles, with a lamellar periosteal reaction and mild lymphadenopathy. Radiographs confirmed soft-tissue swelling and periosteal response. Histopathology identified necrotizing and hemorrhagic tissue with periosteal fibrosis and trabecular bone proliferation, consistent with a chronic organized hematoma—a hemophilic pseudotumor. Postoperatively, the dog received additional plasma transfusion and analgesia. Recovery was uneventful, with full limb function restored within 8 weeks and no recurrence at 20-month follow-up.
Limitations
As a single case report, the findings cannot establish the prevalence or risk factors for pseudotumor formation in hemophilic dogs. Advanced imaging such as MRI, which may better differentiate stages of hemorrhage, was not performed. Additionally, perioperative factor VIII levels were not serially monitored, limiting assessment of coagulation management efficacy.
Conclusions
This report documents the first case of a soft-tissue (intramuscular) hemophilic pseudotumor in a dog, confirmed through CT imaging and histopathology. The lesion’s appearance paralleled human cases, with peripheral rim enhancement and central non-enhancing regions. Surgical excision following factor VIII replacement resulted in complete recovery and no recurrence. Clinicians should consider hemophilic pseudotumor in young, male dogs with known coagulopathies presenting with soft-tissue masses to prevent misdiagnosis as neoplasia and guide appropriate management.
Computed tomographic multiplanar reconstruction images. (A) Sagittal image in soft tissue window, after contrast administration,showing the large heterogeneous soft tissue mass adjacent to the right femur (white arrows). (B) Dorsal plane in bone window showing the lamellarperiosteal reaction along the lateral margin of the right femur (black arrows)
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