Hematological abnormalities are known features of many viral infections and immunization. Influenza A is associated with leukopenia, although it is not reported to cause isolated thrombocytopenia, anemia or pancytopenia in adults.

There is, however, one case report of 67-year-old patient who developed thrombocytopenia and severe neutropenia three weeks after she was vaccinated against influenza.(1) Since influenza vaccine does not contain live virus, its hematological effects presumably relate to the host immune response, rather than to viral replication. In the pediatric age group, there are three reported cases of transient pancytopenia associated with influenza virus infection.(2) Given the high frequency of influenza A infections during the winter months, it is very important to recognize the possible associated hematological findings.

Case Report

A 41-year-old white female with a past medical history of multiple sclerosis (MS) came to the medical center with complaints of cough for three days, fever for two days and myalgias for two days. Her MS had been present since 1987, with occasional exacerbation of sensory symptoms (last episode one year ago), mild ophthalmic involvement only once but was, currently, not on any treatment for MS. She had visited her PMD two days earlier with the same complaints and was advised to take Azithromycin^® and cough syrup. On the next day, she had a fever of 101.2º F with chills and runny nose and went to her local hospital. A chest x-ray was done (reported normal) and the patient was discharged on the same medications. She continued, however, having symptoms, including an episode of dizziness, and came to the emergency room. There was no significant past medical history except MS, no significant past surgical history or family history. The patient is a non-smoker. She was taking Azithromycin^®, Ibuprofen^® and Clonazepam^®.

On physical examination, she was a healthy appearing, fully alert, awake and ambulatory person with congested throat and nose. Chest and abdomen examinations were unremarkable. No lymphadenopathy was present.

Laboratory Findings

Initial laboratory findings: hemoglobin 13.5 gm/dl, hematocrit 39.9%, WBC 3.7 x 10⁹/L with 80% segmented forms, 10% lymphocytes, 8% monocytes and platelets 119 x 10⁹/L.

Chemistries included: Na 135 meq/l, Potassium 3.9 meq/l, CL 97 meq/l, CO₂25 meq/l, BUN 10 meq/l, Creatinine 0.6 meq/l, CPK 62 U/L, LDH 169 U/L, Total Bilirubin 0.4 mg/dl, AST 24 U/L, ALT 24 U/L, Alkaline Phosphatase 34 U/L, Albumin 4.9 gm/l and Globulin 3.5 gm/l.

Urine analysis was unremarkable, as was a chest x-ray.

In the next two days, laboratory findings were: hemoglobin 11.1 gm/dl, hematocrit 31.9%, WBC 2.1 x 10⁹/L with 60% segmented forms, 26% lymphocytes, 13% monocytes and platelets 92 x 10⁹/L.

A rapid test virology study for Influenza was positive from a nasopharyngeal swab.

Course

The patient was treated only with supportive measures, antipyretics and IV fluids. She was not prescribed antibiotics. She was kept on droplet isolation. Her blood counts improved without any intervention. Hemoglobin came up to 12.8 gm/dl, hematocrit rose to 37.1%, WBC 3.0 x 10⁹/L with 70% segmented forms, 23% lymphocytes, 4% monocytes and platelets 130 x 10⁹/L during her hospital stay.