Hematologic mask of infective endocarditis as a cause of fever of unknown origin: a case report

Fever of unknown origin (FUO), despite the wide diagnostic potential of modern medicine, remains a difficult problem for clinicians. Often, making a correct diagnosis requires a comprehensive examination of the patient, as well as the joint work of doctors from different specialties.A 57-year-old male patient was hospitalized due to an episode of loss of consciousness, unmotivated weight loss and daily evening temperature rises to 38-39о C, accompanied by chills and increased sweating. Previously, he was examined by a general practitioner, a cardiologist, and repeatedly by a hematologist. There was no evidence of an infectious disease, arrhythmias, multiple myeloma, lymphoproliferative disorders. Monoclonal gammopathy of undetermined significance (MGUS) was diagnosed. Blood tests revealed neutrophilia (9800 cells/ μl) and moderate anemia. The patient was hospitalized to determine the FUO cause. Heart auscultation revealed a systolic murmur in the mitral valve, which was previously absent. Echocardiography revealed a mobile masses on the mitral valve, severe mitral regurgitation, and therefore infective endocarditis was diagnosed. Empirical antibiotic therapy with ceftriaxone and levofloxacin was administered. Further blood culture revealed growth of a HACEK representative Aggregatibacter actinomycetemcomitans, sensitive to both drugs. Examination established the odontogenic nature of endocarditis. During treatment, stable normothermia and significant blood count improvement were achieved. However, fluoroquinolone therapy led to tendinopathy. Due to persistent grade 3 mitral regurgitation, the patient underwent routine mitral valve replacement. Further follow-up revealed satisfactory condition of the patient.A feature of this case is the atypical course of infective endocarditis, occurring under a hematological mask, which made its diagnosis difficult. When examining a FUO patient, infective endocarditis should be included in the range of possible causes, taking into account not only the typical clinical picture, but also the numerous masks of this disease.