1. Leukopenia
   1. Neutropenia/ Agranulocytosis
      1. Treatment: Removal of offending drug
      2. Most myelotoxic drugs affect all marrow elements
      3. Accelerated removal or destruction of neutrophils
      4. Inadequate or ineffective granulopoeisis
      5. Severe (Agranulocytosis): <500/uL
   2. Granulocytopenia- common
   3. Lymphopenias- less common
2. Reactive Leukocytosis (infectious mononucleosis)
   1. Diagnosis: Positive heterophile reaction (monospot test)
   2. Impaired immunity can have disasterous consequences
   3. Occassionally, reed-Sternberg like cells
   4. Differential: malignant Hodgkin's lymphoma
   5. X-linked lymphoproliferative syndrome
      1. EBV Infection; 50% boys have infection and die
   6. Kissing disease- spread orally
3. Reactive Lymphadentis
   1. Acute nonspecific
      1. nodes tender, abscess: fluctuant
   2. Chronic Nonspecific
      1. follicular hyperplasia (most common)
      2. paracortical hyperplasia
      3. Sinus histiocytosis
   3. Cat Scratch Disease
      1. Self-limited lymphadenitis
      2. Bacterium Bartonella henselae
      3. initially, sarcoid-like (hard) granulomas
      4. Irregular stellate necrotizing granulomas