Non-neoplastic WBC Disorders

• A CBC gives you a total number of WBCs as well as a breakdown of different WBC types
• Neutrophils are the most common WBC and make up 60% of all WBCs
• Neutrophils can survive for 1 day in blood and 5 days in tissue
• Neutrophils work to phagocytose bacteria and fungi
• Lymphocytes make up 30% of WBCs and survive for weeks to years
• Eosinophils make up 2-3% of WBCs, secrete cytokines and survive for 1-1.5 weeks
• Basophils make up 1% of WBCs, release histamine and survive for hours-days
• Monocytes make up 5% of WBCs, phagocytose and present antigens and survive for hours-days
• Bone marrow biopsy of the posterior iliac crest is a key screening test
• Bone marrow aspirate of the sternum can also be done
• Leukopenia is a deficiency of WBCs
• Leukocytosis is an expansion of WBCs
• Neutropenia: the presence of abnormally few neutrophils in the blood, leading to increased susceptibility to infection.
• Neutropenia can be caused by inadequate granulopoiesis or accelerated removal/destruction
• Cyclic neutropenia is caused by regular fluctuations in the number of neutrophils in peripheral blood
• Cyclic neutropenia is associated with ELANE gene mutations and is autosomal dominant
• Cyclic neutropenia can be treated with regular monitoring of blood counts and granulocyte-colony stimulating factor (G-CSF)
• Lymphopenia is less common than neutropenia and can be acquired or congenital
• Left shift is a term used to describe the presence/increased number of immature cells
• Neutrophilia describes circumstances that result in increased neutrophils
• Leukemoid reaction is a form of neutrophilia that involves reactive cellular changes: toxic granulation, Dohle bodies
• Leukoertyrhoblastic response is a form of neutrophilia that involves a granulocytic left shift and an increase in nucleated RBCs. It is indicative of bone marrow stress
• Chronic myeloid leukemia (CML) involves a granulocytic left shift with basophilia
• Neutrophilia is associated with bacterial infections or iatrogenic
• Eosinophilia is associated with allergic disorders, parasitic infections and drug reactions
• Basophilia is rare and usually neoplastic
• Monocytosis is associated with chronic infections and autoimmune disorders
• Lymphocytosis is associated with viral infections and chronic immunologic stimulation
• Infectious mononucleosis leads to peripheral lymphocytosis when the virus replicates in B cells and the CD8+ T cells respond
• Reactive lymphocytes can be distinguished by clumped chromatin, lower nuclear:cytoplasmic ratio, "ballerina skirting" and usually no nucleoli

  
• Blasts can be distinguished by homogenous chromatin, high nucleus:cytoplasm ratio, and prominent nucleoli
• Follicular hyperplasia is due to B cell proliferation. The follicle is no longer limited to the cortex but the mantle zones are still intact

  
• Interfollicular hyperplasia is due to T cell proliferation. Intact follicles are spaced far apart

  
• Follicular hyperplasia is associated with rheumatoid arthritis, secondary syphilis, early HIV infection and toxoplasmosis
• Interfollicular hyperplasia is associated with viral infections, post vaccination, drug reactions and dermatopathic lymphadenitis
• Sinusoidal hyperplasia involves expanded sinuses and increased intrasinusoidal histiocytes

  
• Sinusoidal hyperplasia is associated with Langerhans cell histiocytosis, "Rosai-Dorfman disease", emperipolesis and nodules draining cancer but is most often due to no known cause
• Non-necrotizing granulomas are associated with sarcoidosis and nonspecific reactions to malignancy
• Necrotizing granulomas are associated with fungal infections, tuberculosis and cat-scratch disease
• Cat-scratch disease is caused by Bartonella henselae, causes regional lymphadenopathy and stellate or serpentine necrotizing granulomas with central neutrophils