The diagnosis for mystery case #3

We gave out the result:

21.0%                 Segmented neutrophil
0.3%                   Eosinophil
0.5%                   Basophil
61.7%                 Lymphocyte (With comment: “activated”)
5.3%                   Monocyte
0.5%                   Myelocyte
10.3%                 Other (with comment: “Atypical mononuclear cells with immature appearance (Virucytes?)) “

I called the department and asked if they suspected infectious mononucleosis. I have seen mononucleosis-cells before, but as I recall they look more like large, activated lymphocytes.

The answer was yes, and 2 days later, the diagnosis was confirmed by a positive Epstein -Barr test (EBV).

Normally we do not have this kind of “benign” disease at Rigshospitalet. Usually, we look for malignant haematological diseases.

In 1923, Downey divided the atypical lymphocytes into 3 types. But of course the lymphocytes seen in infectious mononucleosis cannot be distinguished from those seen in other viral diseases.

I think the cells in the “Other” cell class are very similar to Downey Cells.

Classification of atypical lymphocytes can also be done according to Wood and Frenkel (1967).

Infectious mononucleosis is an acute clinicopathological syndrome resulting from primary infection by the EBV. It predominantly occurs in children and young adults. Common clinical features are fever, pharyngitis, Lymphadenopathy, and splenomegaly. The disease is characterized by atypical or activated lymphocytes, mainly activated T lymphocytes, produced as part of the immunological response to EBV-infected B lymphocytes.

This book was very useful to me. It explains more about Downey’s classification and shows photos; A color atlas and instruction manual of peripheral blood cell morphology. By Barbara H. O’Connor.

I had infectious mononucleosis diagnosed at the age of 12, and it was indeed a very unpleasant and painful period ;O).

Margit Grome

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