Prolonged lymphopenia in a patient with lymphoma and severe Pandemic influenza A H1N1 2009 virus infection

Objective To describe the clinical course of a confirmed influenza A Pandemic (H1N1) 2009 virus infection in a patient with lymphoblastic lymphoma on chemotherapy. Design Case report. Setting Instituto Nacional de Cancerologia located in Mexico City, a national referral center for cancer patients. Patient and results A 15-year-old boy, with lymphoblastic lymphoma on chemotherapy. Oseltamivir 75 mg BID was started within 24 hour of first symptoms. The patient developed respiratory failure despite oseltamivir therapy; he presented a prolonged clinical course with severe lymphopenia and deteriorated every time oseltamivir was stopped while lymphopenia persisted. Oseltamivir was reassumed twice; in the second course, rimatadine was added. Genetic study of the virus showed 100% identity for AH1N1SW, and no H274Y mutation for oseltamivir resistance was found. Clinical recovery was apparent until he presented lymphocyte reconstitution after 35 days of disease while still on antiviral therapy. Conclusion This case exemplifies the need to sustain antiviral therapy while patient continues with severe lymphopenia. Lymphocyte count could be used as a surrogate marker to prolong antiviral therapy in patients with severe lymphopenia and clinically symptomatic Pandemic (H1N1) 2009 infection. This case also highlights the importance of treating patients based on clinical grounds and the variability of rRt-PCR test for H1N1.