Elevated White Blood Cell Count with Reactive Leukocytosis in Setting of Fungal Infection

Case at a Glance

A 38-year-old male presented with leukocytosis (WBC 15,000) requiring peripheral blood smear evaluation to rule out hematologic malignancy versus reactive process in the setting of concurrent fungal infection.

Patient's Story

The patient presented for routine laboratory work which revealed an elevated white blood cell count of 15,000. He reported having an active fungal infection at the time of testing. Given the significant leukocytosis, his physician ordered a peripheral blood smear to further characterize the elevated white cell count and rule out underlying hematologic disorders.

Initial Assessment

Laboratory findings showed leukocytosis with WBC count of 15,000 (normal range 4,000-11,000). The patient had no other acute symptoms reported aside from the known fungal infection. Physical examination findings were not documented but presumed consistent with localized fungal infection.

The Diagnostic Journey

Peripheral blood smear was performed to differentiate between reactive leukocytosis versus primary hematologic malignancy. The smear revealed reactive-appearing leukocytosis with mild granulocytic left shift and occasional atypical lymphocytes. No blast cells or other morphologic features suggestive of acute leukemia were identified.

Final Diagnosis

Reactive leukocytosis, likely secondary to fungal infection. The pathologist noted that while the current findings suggest a reactive process, persistent or chronic leukocytosis would warrant molecular studies including BCR-ABL rearrangement, JAK2, CALR, and MPL mutations to evaluate for myeloproliferative neoplasms.

Treatment Plan

Treatment of the underlying fungal infection was continued. Close monitoring of complete blood count was recommended to ensure resolution of leukocytosis following treatment of the infection. If leukocytosis persists despite adequate treatment of the fungal infection, further hematologic workup including molecular studies would be indicated.

Outcome and Follow-up

Patient was scheduled for follow-up appointment in one week to reassess clinical status and repeat laboratory studies. The consulting hematopathologist confirmed that fungal infections can indeed cause reactive leukocytosis, though the pattern observed was more typical of bacterial infections. Patient was counseled that immune responses can vary between individuals and that clinical correlation with infection treatment response would guide further management.