Systemic polyarteritis nodosa is a vasculitis characterized by inflammation and fibrinoid necrosis of medium and small arteries, with a global incidence of 0.7/100,000 and a prevalence of 6.3/100,000. Its cause is as yet unknown, and it affects both children and adults. The clinical presentation tends to be insidious and vague in its initial stages. Cardiac involvement is one of the signs of severity, with coronary artery impairment and aneurysmal lesions of varying degrees. The consequent heart failure and acute myocardial infarction are complications which increase mortality. Without treatment, five-year survival is 13%. Medical treatment is aimed at halting the inflammatory process and treating the consequences of the dysfunction of various organs and systems. We present a case of an eight-year-old boy with polyarteritis nodosa who developed giant aneurysms of the coronary arteries with severe cardiac dysfunction and multisystem impairment. The proper diagnosis and prompt treatment achieved clinical recovery and early survival.