A 73-year-old woman with a personal history of bronchial asthma treated with bronchodilators on demand. She reported no cardiovascular risk factors. The patient came to the hospital with bronchial hyperresponsiveness secondary to respiratory infection. In the anamnesis she reported oppressive back pain with sweating and dyspnoea for 8 months, triggered by moderate exertion, which subsided with rest and had not changed during this time. Cardiac auscultation was rhythmic, with a third sound, a fluctuating systolic and diastolic murmur and signs of heart failure. Pulmonary auscultation revealed rhonchi and wheezing compatible with the bronchial hyperresponsiveness that led to admission. Laboratory tests showed anaemia with a slight increase in acute phase reactants. Cardiac biomarkers were negative. The ECG was normal and the chest X-ray showed cardiomegaly, not present in a previous one a year earlier. With the initial suspicion of bronchial hyperresponsiveness, stable exertional angina and secondary heart failure, an echocardiogram was requested which showed a mass measuring 4 x 5 cm dependent on the left atrium and which protruded in diastole from the fossa ovalis into the ventricle, producing mitral stenosis. Subsequently, a cardiac catheterisation was performed in which no angiographically significant coronary lesions were observed. On suspicion of atrial myxoma, the patient underwent surgery and the diagnosis was confirmed by histology. Four months after surgery the patient is asymptomatic and there is no evidence of recurrence.