Differentials
Leukaemoid reaction
SIGNS / SYMPTOMS
There are no specific clinical differentiating features.
INVESTIGATIONS
High WBC count resolves once underlying condition (e.g., infection) is treated.
Benign neutrophilic leukocytosis
SIGNS / SYMPTOMS
There are no specific clinical differentiating features.
INVESTIGATIONS
Fluorescence in situ hybridisation (FISH): negative for BCR::ABL1 fusion gene; absence of left-shifted WBC differential.
Atypical CML
SIGNS / SYMPTOMS
There are no specific clinical differentiating features.
INVESTIGATIONS
Cytogenetics, FISH, quantitative polymerase chain reaction (qPCR): negative for BCR::ABL1 fusion gene; thrombocytopenia often prominent.
Chronic myelomonocytic leukaemia
Essential thrombocythaemia
SIGNS / SYMPTOMS
More indolent clinical course.
Unlikely to transform into acute leukaemias.
INVESTIGATIONS
FISH: negative for BCR::ABL1, presence of JAK2, CALR, or MPL mutation.[40]
FBC: high platelet count.
Important to differentiate from early myelofibrosis.
Ph+ acute lymphoblastic leukaemia
SIGNS / SYMPTOMS
Much more rapid disease course.
Patients often present with anaemia and thrombocytopenia. B symptoms are common (e.g., fever, night sweats, and weight loss).
INVESTIGATIONS
Peripheral blood smear: lymphoid blasts.
Bone marrow examination and flow cytometry show terminal deoxynucleotidyl transferase-positive (TdT+) immature B lymphoblasts.
FISH: positive for 190-kDa BCR::ABL1 fusion.[1]
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