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An isolated myeloid blast crisis presenting as optic nerve sarcoma in a patient with chronic myeloid leukaemia treated with imatinib

A 34-year-old female with chronic-phase chronic myeloid leukaemia (CML) was treated with 400 mg/d of imatinib. After 6 months of treatment, she achieved a complete cytogenetic response (CCyR), but no major molecular response. Twelve months later, the patient suddenly developed severe left eye pain, exophthalmos and blurred vision accompanied by headache and emesis. The vision in her left eye rapidly deteriorated to light perception only. Fundoscopy of the left eye showed papilloedema. Magnetic resonance imaging of the brain revealed a solitary left optic nerve tumour (arrows). Lumbar puncture showed an elevated total cell count (93 cells/ll). The blast cells were positive for CD13, CD33 and CD117, but negative for CD3, CD19 and CD20 by flow cytometry. She was diagnosed with a myeloid blast crisis presenting as a left optic nerve sarcoma while maintaining a CCyR in the bone marrow cells. She underwent eight cycles of intrathecal chemotherapy comprising cytarabine (40 mg), methotrexate (15 mg) and dexamethasone (4 mg), plus whole and focal brain irradiation (50 Gy). Magnetic resonance imaging showed disappearance of the optic nerve tumour, and lumbar puncture showed no residual blast cells in the cerebrospinal fluid. After chemoradiation therapy, all of her symptoms were relieved, but the left visual acuity did not recover. She received an allogeneic peripheral blood stem cell transplant from a human leucocyte antigen 1 locus-mismatch sibling donor. After stem cell transplantation, she developed severe thrombotic microangiopathy and died. Blast crisis presenting as an isolated optic nerve tumour is rare: although there are several published reports of a central nervous system blast crisis in CML patients on imatinib therapy, the lesions were multiple or diffuse. Imatinib does not penetrate the blood brain barrier. Therefore, the possibility of a central nervous system relapse and blast crisis in CML while on treatment must be kept in mind.