Tuberous sclerosis (TS) is a rare congenital disease characterized by proteiform symptoms that effect the skin and the central nervous system. Occasionally morphofunctional anomalies of other organs such as the kidneys, lungs and heart are present. The clinical picture of the illness varies among patients, and diagnosis is based primarily on cutaneous or nervous system manifestations. During the last ten years, however, some cases of prenatal diagnosis have been reported. The literature reports very few cases of tuberous sclerosis with arrhythmias as the initial symptom. The case described refers to a newborn who presented with supraventricular arrhythmias, refractory to the common antiarrhythmic drugs; a subsequent M-mode and two-dimensional echocardiogram showed a small roundish mass in connection with the chordae tendinae of the mitral valve (rhabdomyoma). We initially diagnosed TS based on the appearance of achromic smooth spots of the skin. The onset of convulsions and a CAT scan that identified numerous calcified endocerebral nodules confirmed the diagnosis of tuberous sclerosis.