Case Presentation: The following case highlights a rare complication, pancytopenia, in a common disease entity, Influenza A. A 73-year-old Mandarin speaking male with a past medical history of diabetes presented to the emergency department following an outpatient visit which found abnormal laboratory values. On initial assessment, the patient had stable vital signs and physical exam was solely notable for clear nasal discharge. Laboratory evaluation displayed leukopenia of 1,400 K/uL with lymphocytic predominance, normocytic anemia of 8.5 g/dL, and thrombocytopenia of 15,000 K/uL. On further history, the patient had been in his usual state of health until two days prior to presentation when he developed rhinorrhea, sore throat, dry cough, and decreased appetite. In the ED, nasopharyngeal swab was obtained that confirmed Influenza A virus. The patient was initiated on oseltamivir and supportive treatment with improvement of viral symptoms. Multiple laboratory and imaging tests were obtained to evaluate for alternate infectious, malignant, or immunologic etiologies that could be causing the pancytopenia, of which all results were normal. The hematologic abnormalities gradually improved as the viral symptoms resolved, suggesting that the pancytopenia was secondary to Influenza A.

Discussion: Influenza is a major cause of morbidity and mortality worldwide, with the CDC estimating an approximate of 425,000 influenza-related hospitalizations annually since 2010. Individual hematologic abnormalities are often noted in patients with influenza; however, pancytopenia has rarely been documented in the literature, with majority of cases seen in the pediatric population. The mechanism of pancytopenia in influenza may involve viral inhibition of erythroid and granulocytic cell lineages via infection of the bone marrow, however, additional research is needed to verify this finding.

Conclusions: Regardless of etiology, pancytopenia in influenza is a serious complication of a common condition that must be recognized, with the understanding that laboratory values will recover with improvement of the viral syndrome.