This could be a case of Ph+ BCR-ABL+ CML with a rare fusion transcript that cannot be detected by current PCR testing. Very rare, almost hypothetical, but worth of a trial of imatinib 400 mg once daily. If it works, it works very quickly, the cost of the generic is low and toxicity is negligible.
Deletions of the long arm of chromosome 11, though non specific, recur in several Phneg CMN. Some patients have responded to Ruxolitinib. If Imatinib fails, I would try Ruxo.
But I’m afraid that one should plan allogeneic stem cell transplantation, as soon as possible, if the patient is eligible, any donor but cord blood, myeloablative, with Cyclophosphamide after stem cell infusion.
Good Luck!