Case Presentation: A 25-year-old female with no significant past medical history presented to the emergency department after having altered mentation while at home. As per her significant other, she had a runny nose, fatigue, and cough for two days. On initial assessment, vital signs showed low grade fever of 100.4 F, tachycardia up to 110/minute. Her blood pressure and finger stick glucose were normal. On physical exam, she was alert and oriented only to herself; the rest of the exam was normal: no skin rash, nasal discharge or signs of nuchal rigidity were present. Initial laboratory evaluation displayed pancytopenia; white blood cell count 1.7k/ul (4.8 – 10.8k/ul), neutrophil count 1.0k/ul (1.8-7.7 k/ul), hemoglobin 5.9g/dl (12.2-15.3g/dl), platelets 96k/ul (150-400k/ul). Blood gas showed mildly elevated lactate levels. Infectious work-up including blood, urine, and respiratory cultures were negative. Chest X-ray and lumbar puncture was negative for infectious etiology. Nasopharyngeal swab confirmed Influenza A virus. The patient was initiated on oseltamivir and supportive treatment with improvement of her mental status and viral symptoms. Prophylactic antibiotics were started to cover for superimposed bacterial infection, which were later discontinued. Work up to evaluate for alternate infectious, malignant, or infectious etiologies that could cause pancytopenia were negative. Hematologic abnormalities gradually improved as viral symptoms resolved, suggesting that pancytopenia was secondary to Influenza A.
Discussion: Influenza is a major cause of morbidity and mortality worldwide. The CDC estimates that influenza was associated with more than 48.8 million illnesses, more than 22.7 million medical visits, 959,000 hospitalizations, and 79,400 deaths during the 2017–2018 influenza season. Influenza virus-induced pancytopenia in adults has rarely been documented in the literature. Majority of the cases were seen in pediatric population with first case reported in 1998. The mechanism for pancytopenia may involve viral infections causing direct and indirect damage to hematopoietic stem and progenitor cells (HSPCs) and the surrounding tissue. Direct pathogenic effects depend on viral tropism and viral cycle, but the complex interactions between viruses, HSPCs, and the bone marrow (BM) microenvironment are underappreciated at the moment. While considerable insight has been gathered regarding the regulation of BM output by general inflammatory processes and bacterial infections, less is known about the specific regulation of hematopoiesis by viral infections.Viral-induced cytopenias usually resolve in a median of 12 days after onset of symptoms, which is a significantly shorter duration for recovery when compared to other etiologies.
Conclusions: Pancytopenia in influenza is a serious, but rare, complication that must be recognized, with the understanding that laboratory values recover with improvement of viral symptoms.