This is an 83-year-old male with history of chronic kidney disease, hypothyroidism and past history of anemia, coming for follow-up of anemia.  At this time patient has fatigue and loss of appetite.

His current CBC at the time of presentation:
WBC-------------       4600/mcL (normal)
Hemoglobin----          10 g/dL (low)
MCV--------------        113 fL     (elevated)
Platelet count-  153,000/mcL (normal)

Differential count:
Lymphocytes 65% (elevated)
Neutrophils 32%    (low)
Monocytes 3%      (low)

The findings here are typical for chronic lymphoproliferative disorder of NK cells (CLPD-NK), the NK cells counterpart of T–large granular lymphocyte leukemia.  These are indolent and sometimes clonal lymphoproliferations that may cause progressive cytopenias in the context of autoimmune disease.  About 10 months after initial diagnosis, the patient exhibited progressive cytopenias with pancytopenia.

Learning points:

1. NK cells express CD2 and CD7 but are negative for CD3, CD4 and CD5.  There may be variably positive for CD8.
2. Persistent elevated absolute lymphocyte count of >2000/mcL for 6 months or more is seen in most patients.
3. STAT3 mutations are common in these patients and are associated with more pronounced clinical manifestations