Pancytopenia: the elusive diagnosis of HLH

- We recently talked about a case of pancytopenia. Here's an approach to bone marrow pathology:

Infiltrative - Any hematological malignancy (includes myelofibrosis) 
                - Metastatic solid tumors
                - Inflammatory: sarcoid, amyloid
                - Invasive infections 

Dysplasia - Myelodysplastic syndrome 

Aplasia - Immune 'aplastic anemia' 
            - Toxins, drugs or chemotherapy
            - Radiation 
            - Nutritional - VB12, folate deficiency
            - Viral (HIV, HBV, HCV, EBV, CMV, etc.) or sepsis 

- We reviewed a rare case of pancytopenia, hemophagocytic lymphohistiocytosis, where the immune system becomes overactive because of a lack of functioning NK cells and CD8+ T cells
Diagnostic criteria:
1) Fever
2) Splenomegaly
3) Cytopenia in at least 2 cell lines
4) Hypertriglyceridemia and/or hypofibrinogenemia
5) Tissue demonstration of hemophagocytosis (not specific)
Additional criteria include low/absent NK cell function, very high ferritin levels, or elevated CD25