Case Presentation: A 42-year-old female with a past medical history of end stage renal disease from focal segmental glomerulosclerosis on hemodialysis for the past four years, presented to her cardiologist with worsening dyspnea on exertion and a feeling of “increased fluid in her lungs”. An outpatient transthoracic echocardiogram (TTE) was obtained, which showed a normal ejection fraction and lesions on the mitral and aortic valves highly suggestive of vegetations. The patient was hospitalized with concern for endocarditis. On admission, the patient was afebrile. Physical examination was notable for hypertension, bilateral inspiratory pulmonary crackles, and a holosystolic murmur in the mitral area. Her leukocyte count was normal. A repeat TTE showed severe mitral annular calcification, moderate-severe mitral stenosis, and several mobile lesions on the mitral and aortic valves. Given dialysis patients’ increased risk for infective endocarditis, with some studies showing 50-60 times the incidence compared to the general population, an extensive work-up was undertaken for infectious etiologies. Blood cultures did not grow any organisms. Bartonella and Coxiella serologies were negative, and a β-D-Glucan assay was indeterminate. Despite negative blood cultures, the inpatient care team successfully advocated for trans-esophageal echocardiography (TEE) for further characterization of the valvular lesions. TEE revealed severe mitral valve calcifications, focal calcifications of the aortic valve, and moderate mitral stenosis, but no evidence of endocarditis. The diagnosis of mitral annular calcification with moderate mitral stenosis was made. Given the non-severe degree of her stenosis, mitral valve replacement or repair was not recommended by the cardiothoracic surgical service. The patient received routine care and was discharged from the hospital. Her outpatient cardiologist recommended echocardiograms every six months to monitor for progression of her mitral stenosis.

Discussion: Mitral annular calcification (MAC) is a chronic degenerative condition that is associated with age, chronic kidney disease, diabetes, dyslipidemia, hypertension, and tobacco use. The pathophysiology of MAC is thought to be a product of endothelial disruption, chronic inflammatory cell infiltration, and elevated calcium-phosphorus product. Observational studies have found MAC to be prevalent in over one third of patients who have been on hemodialysis for more than three years. Advanced cases of MAC can result in left ventricular inflow obstruction, symptomatic mitral stenosis, and increased risk of arrhythmias. MAC is a marker of atherosclerotic disease and is associated with 60% increased incidence of cardiovascular disease related death and 30% increased incidence of all-cause mortality. This case highlights the potential for mitral annular calcification to mimic vegetations on TTE, and therefore the possibility for MAC to be misdiagnosed as endocarditis. The clinical suspicion for MAC should be high in ESRD patients presenting with valvular abnormalities, regardless of their age.

Conclusions: Although mitral annular calcification is associated with older age, young patients on hemodialysis are at greatly increased risk for developing this condition. Mobile calcified lesions can be mistaken for endocarditis on TTE, creating a unique diagnostic challenge. TEE is a useful modality to differentiate mobile masses on the mitral valve.

IMAGE 1: TEE midesophageal long axis view notable for hyperechoic, mobile masses on the mitral valve.

IMAGE 2: 3D reconstruction of TEE image of mitral valve, notable for significant calcification, thickened mitral valve leaflets and moderate mitral stenosis