Teaching Case

A 24-year-old man, known to have haemophilia A, had a lytic lesion in the left body of the mandible 10 years ago, which was managed conservatively. He came to our department for a routine follow-up CT scan of the mandible.

A CT reconstruction of the mandible with a high slice thickness, dated 10 years ago, revealed a well-defined lobulated lytic lesion in the left body of the mandible with a narrow zone of transition. The lesion involved the alveolar processes (Figure 1). A 3D CT reconstruction of the mandible also showed a well-defined lytic lesion (Figure 2).

However, the present CT scan indicates complete resolution of the previously identified lesion in the mandible. The alveolar processes and the teeth were found to be normal in the region that was previously affected (Figures 3, 4a and 4b).

Haemophilia A is an X-linked disorder exclusively found in males [1]. Pseudotumours can be categorised into three types based on their site of occurrence: type 1 (soft tissue), type 2 (subperiosteal), and type 3 (intra-osseous) [2]. Osseous pseudotumor, a rare manifestation in haemophilia, results from repetitive haemorrhage into the bones [3,4]. Pseudotumours are typically asymptomatic, and their presentation may be due to mass effect or acute bleeding into the lesion [5]. Trauma is the usual inciting factor in most cases.

Pseudotumours are slow-growing expansile lesions with well-defined, narrow transition zones, and sclerotic margins. They are usually multiloculated. In tubular bones, they may involve epiphysis or metaphysis with endosteal scalloping, cortical thinning, and pathological fractures [4]. The most commonly involved sites are the femur, pelvic bones, tibia, and the small bones of the hand. Occasionally, a soft tissue component may be present [6]. Involvement of the mandible is extremely rare [1]. CT is valuable for assessing bones and their anatomical extent, while MRI depicts soft tissue involvement. Signal intensity on MRI depends on the stage of the blood products. It does not show enhancement [5].

Common differentials for a lytic lesion involving the mandible include benign lesions such as aneurysmal bone cysts, Langerhans cell histiocytosis, brown tumours, and haemangiomas. Malignant lesions that need to be considered include metastasis, Ewing sarcoma, and osteosarcoma [3]. However, a history of haemophilia is sufficient for the diagnosis, and histopathological confirmation is deemed unnecessary, as this pathology is considered a “touch me not” lesion [7].

Prevention is the best approach to managing a pseudotumor. However, once it occurs, the initial management involves factor correction and immobilisation [2]. Surgical management is reserved for patients with refractory lesions [6]. Aspiration, curettage, enucleation, and resection are available surgical options [2]. Most cases with mandibular involvement which have been reported, were managed surgically, and spontaneous resolution of a mandibular pseudotumor on conservative management is exceedingly rare [1,6].