Rapid interval progression of familial atrial myxoma despite negative screening.

A 14-year-old girl with biopsy-proven extracardiac myxomas presented with recurrent cardioembolic stroke due to a rapidly developing giant left atrial myxoma. A pathogenic PRKAR1A variant and maternal history confirmed familial Carney complex. Urgent surgical excision prevented further embolization, emphasizing the aggressive and unpredictable nature of familial cardiac myxomas.