Proptosis in orbital myeloid sarcoma: A precursor to acute leukaemia

Myeloid sarcoma is a rare, aggressive presentation of acute myeloid leukemia which tends to affect bones and soft tissue. It is usually seen in children, and has a poor prognosis. We report a case of orbital myeloid sarcoma presenting with unilateral proptosis in a young adult who subsequently developed acute myeloid leukaemia. An 18-year-old male presented with sudden, progressively increasing right eye swelling over two weeks. Examination revealed right eye proptosis, with a positive relative afferent papillary defect and a right eye visual acuity of 6/60, pinhole 6/18. The right fundus showed optic disc hyperemia, tortuous veins and choroidal folds. The left eye was normal. On initial examination, computed tomography (CT) of the brain and orbit showed an enhancing mass at the lateral aspect of the right orbit measuring 3.8 × 2.1 cm, with optic nerve displacement. Right lateral orbitotomy and excisional biopsy yielded a tissue diagnosis of myeloid sarcoma. The peripheral blood smear was normal at this time. The patient defaulted treatment but presented again three months later with right eye massive proptosis and loss of vision. A repeated CT scan showed a large lobulated mass measuring 104.5mm × 87.21mmm × 77.25mm occupying the right orbit, with destruction of the bony orbital walls and intracranial extension. A repeat full blood picture and bone marrow aspiration showed 30% blast cells, consistent with the diagnosis of acute myeloid leukemia. Patient was started on chemotherapy and radiotherapy. The tumour reduced in size after five cycles, but unfortunately, patient passed away due to brain metastases