Eosinophilia Pearls

Today's summary statement: An elderly man with a history of untreated non-small cell lung cancer presents with subacute, progressive shortness of breath found to be hypoxic with a new severe peripheral eosinophilia in the setting of significant progression of his metastatic lung disease.

A basic pearl: NAACP is a mnemonic for peripheral eosinophilia
  Addison's Disease (hypoadrenalism)
  Connective tissue diseases
  Parasitic infections

Keeping things fresh with a freshwater pearl: the differential for eosinophilia with hypoxia can be broadened to also include:
  Acute eosinophilic pneumonia
  Chronic eosinophilic pneumonia
  Hypereosinophlic syndrome

And to end on a Mother of Pearl pearl: Tumor-associated tissue eosinophilia (TATE) may provide insight towards prognosis, as demonstrated in colorectal cancer by Davis et al 2014, where a beneficial influence of eosinophils in diverse tumors was found to be independent of other standard prognostic factors.  We are still left questioning whether peripheral eosinophilia (rather than eosinophils in the tumor tissue itself) can serve as a prognostic factor as well.