A 67-year-old male complained of fever & weight loss. A CBC was performed.

His complete blood count was  Hb=12 g/dl, WBC = 55,290/cmm  &  Platelets=202,000/cmm. His leucocyte count  fluctuated in the range of 52,000-55,000 /cmm. He was referred to a hematologist for persistently high leucocyte count & peripheral smear showed neutrophilic leucocytosis. 

Labortaory investigations revelaed a high Leukocyte alkaline phosphatase (LAP) score. Serum LDH was within normal limits. Cytogenetics investigatons did not reveal BCR-ABL fusion, nor were mutations detected in JAK2 or Calreticulin genes. Infectious causes were clinically ruled out. 

A clinical diagnosis of chronic neutrophilic leukemia was entertained.

However, a bone marrow trephine biopsy surprisingly revealed a plasma cell neooplasm with lambda light chain restriction as shown in this image set. His serum protein studies revealed a 'M' band with IgA lambda monoclonal gammopathy. Skeletal survey revealed lytic bony lesions. 

The findings in this case higlights how plasma cell myeloma may present as a leukemoid reaction. Testing for serum paraprotein is also important in cases with profound neutrophilia.