Neutrophilia

•    Common causes:

o    Bacterial infection

o    Inflammation

o    Steroids

o    Stress

o    Myeloproliferative disorders (e.g. CML, PV)

•    Left shift: ↑ immature granulocytes (bands, metamyelocytes)

o    Seen in infection or marrow stress

Neutropenia

•    Definition: neutrophils <1.5 × 10⁹/L

•    Severe risk: ANC < 0.5 × 10⁹/L → high infection risk

•    Causes:

o    Viral infections (e.g. EBV, HIV)

o    Bone marrow suppression: chemotherapy, radiotherapy

o    Aplastic anaemia

o    Drugs (e.g. carbimazole, clozapine, sulfasalazine)

o    Congenital neutropenia

Lymphocytosis

•    Causes:

o    Viral infections: EBV, CMV, hepatitis

    Atypical lymphocytes: strongly suggest EBV

o    Pertussis (whooping cough)

o    Chronic lymphocytic leukaemia (CLL)

    Smudge cells on blood film

Lymphopenia

•    Causes:

o    HIV

o    Steroids

o    SLE

o    Chemotherapy / Radiotherapy

o    Severe malnutrition

Eosinophilia

•    Mnemonic — NAACP:

o    Neoplasia

o    Allergy/Asthma

o    Addison’s disease

o    Collagen vascular disease (e.g. vasculitis)

o    Parasites (especially helminths)

Basophilia

•    Causes:

o    Chronic myeloid leukaemia (CML) (with eosinophilia and neutrophilia)

o    Chronic inflammation

o    Allergy

o    Hypothyroidism

Leukoerythroblastic Blood Film

•    Definition: presence of immature myeloid cells + nucleated red cells

•    Suggests:

o    Bone marrow infiltration: metastatic cancer, myelofibrosis

o    Myelophthisis

o    Also seen in severe sepsis or haemolysis

Approach to Abnormal White Cell Counts

•    Stepwise approach:

o    Differentiate reactive (infection/inflammation) vs malignant (leukaemia/lymphoma) vs marrow failure

•    Investigations:

o    Blood film: morphology clues

o    Infection screen: viral PCR, cultures

o    Inflammatory markers: CRP, ESR

o    Autoimmune panel: ANA, ENA, dsDNA

o    B12, folate (deficiency can affect all lineages)

o    Bone marrow biopsy: if persistent unexplained changes or cytopenias