Differentials
Polycythaemia vera
SIGNS / SYMPTOMS
Aquagenic pruritus (itching after a shower), plethora.
INVESTIGATIONS
Peripheral blood smear: absence of leukoerythroblastosis.
CBC: erythrocytosis; red blood cell mass and plasma volume elevated.
Essential thrombocythaemia
Chronic myeloid leukaemia
SIGNS / SYMPTOMS
May be no differences in signs and symptoms.
INVESTIGATIONS
Fluorescence in situ hybridisation (FISH) or polymerase chain reaction (PCR): positive for Philadelphia chromosome (BCR::ABL1 fusion gene).
Myelodysplastic syndrome (MDS)
SIGNS / SYMPTOMS
Absence of splenomegaly.
INVESTIGATIONS
Bone marrow aspiration and biopsy with flow cytometry and cytogenetic analysis: dysplastic bone marrow with variable degrees of peripheral blood cytopenia (with or without monocytosis) suggests MDS.
Mast cell disease (systemic mastocytosis)
SIGNS / SYMPTOMS
Dermatographia or skin rash.
INVESTIGATIONS
Serum tryptase level: elevated.
Malignant histiocytosis
SIGNS / SYMPTOMS
May be no differences in signs and symptoms.
INVESTIGATIONS
Bone marrow aspirate and biopsy: infiltration by malignant histiocytes.
Acute myeloid leukaemia
SIGNS / SYMPTOMS
Symptoms (constitutional, bleeding, infections) are more acute. Moderate to massive splenomegaly is less common than in primary myelofibrosis.
INVESTIGATIONS
Bone marrow aspiration and biopsy: bone marrow hypercellularity and infiltration by blasts; blasts >20%, Auer rods, morphological description of type of blast.
Immunophenotyping and molecular studies: blasts express surface antigens and molecular markers that help to identify their specific lineage.
Peripheral blood smear: blasts on blood film, presence of Auer rods.
Acute lymphoblastic leukaemia
SIGNS / SYMPTOMS
Symptoms (constitutional, bleeding, infections) are more acute. Moderate to massive splenomegaly is less common than in primary myelofibrosis.
INVESTIGATIONS
Bone marrow aspiration and biopsy: bone marrow hypercellularity and infiltration by lymphoblasts.
Immunophenotyping and molecular studies: blasts express surface antigens and molecular markers that help to identify their specific lineage.
Peripheral blood smear: leukaemic lymphoblasts.
Hairy cell leukaemia
SIGNS / SYMPTOMS
May be no differences in signs and symptoms.
INVESTIGATIONS
CBC: lymphocytosis and absence of monocytes.
Bone marrow aspiration and biopsy: presence of hairy cells in the bone marrow.
Flow cytometry: reveals a B-cell phenotype lacking CD5 and CD23, while expressing CD103 and cyclin D1.
Immunohistochemical analysis: may reveal BRAF-V600E mutation.
Peripheral blood smear: presence of hairy cells.
Hodgkin's lymphoma
SIGNS / SYMPTOMS
Lymphadenopathy more common in lymphomas.
INVESTIGATIONS
Lymph node biopsy: Hodgkin's cells within an appropriate background cellular milieu.
Non-Hodgkin's lymphoma
SIGNS / SYMPTOMS
Lymphadenopathy more common in lymphomas.
INVESTIGATIONS
Lymph node biopsy: positive for non-Hodgkin's lymphoma.
Multiple myeloma
SIGNS / SYMPTOMS
Symptoms of hyperviscosity and bone pain.
INVESTIGATIONS
Serum and urine protein electrophoresis: serum M-protein (IgG or IgA) ≥30 g/L (≥3 g/dL); urine monoclonal protein ≥500 mg/day; hypogammaglobulinaemia.
Serum and urine immunofixation assay: paraprotein band (IgG, IgA, IgM, IgD, or IgE; and kappa or lambda light chain).
Serum free light-chain assay: increased concentration of free light chains.
Bone marrow aspirate and biopsy: monoclonal plasma cell infiltration in the bone marrow ≥10%.
CT scan and skeletal survey: osteolytic lesions and/or pathological fractures.
Hyperparathyroidism
SIGNS / SYMPTOMS
May be no differences in signs and symptoms.
INVESTIGATIONS
High-normal to elevated calcium; decreased vitamin D; high-normal to elevated parathyroid hormone (PTH).
Renal osteodystrophy
SIGNS / SYMPTOMS
May be no differences in signs and symptoms.
INVESTIGATIONS
Urea, creatinine: elevated.
Radiological studies: osteopenia.
Vitamin D deficiency
SIGNS / SYMPTOMS
May be no differences in signs and symptoms.
INVESTIGATIONS
Decreased vitamin D levels.
Systemic lupus erythematosus (SLE)
SIGNS / SYMPTOMS
Skin, joint, and mucosal manifestations of SLE.
INVESTIGATIONS
Anti-double-stranded DNA.
HIV infection
SIGNS / SYMPTOMS
Opportunistic infections.
INVESTIGATIONS
Anti-HIV antibody: positive.
CD4 count: decreased CD4 count.
Presence of HIV viral load.
Tuberculosis
SIGNS / SYMPTOMS
Cough and haemoptysis.
INVESTIGATIONS
Positive tuberculin skin testing; abnormal chest x-ray; and positive microbiological tests.
Metastatic cancer in the bone marrow
SIGNS / SYMPTOMS
May be no differences in signs and symptoms.
INVESTIGATIONS
CT scans, bone survey, tumour markers: indicate metastatic spread.
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