RASopathies: From Noonan to LEOPARD Syndrome

The authors appreciate the interest in the case report we published in Revista Española de Cardiologı́a concerning the observation of the Brugada electrocardiographic (ECG) pattern in a patient with hyperkalemia. We likewise welcome the introduction of the concept of phenocopy, an expression with which our finding is compatible.We also consider it opportune to stress that both the latest consensus on ECG diagnosis of Brugada syndrome and the introduction of the term phenocopy are more recent than the online publication of our case report in 2011. The definitions of the ECG patterns that are typical of Brugada syndrome and those that mimic this syndrome in the presence of serum electrolyte disturbances were introduced subsequent to our publication. It is important to highlight reasons for attributing the changes observed in the ECG to hyperkalemia rather than to the acidosis and hyponatremia also observed in our patient. Reports of Brugada phenocopy associated with hyponatremia and acidosis have described the development of pseudo J waves in the QRS complex and ST segment depression in leads other than right precordial leads. These are precisely the features that differentiate this ECG pattern from type 1 Brugada pattern. Other possible causes (hyperglycemia, drugs, fever, and myocardial ischemia) were ruled out in the case discussed in our report. We appreciate any contribution that aids in the understanding of the mechanisms involved in the induction of ECG patterns mimicking Brugada syndrome (phenocopies) and other patterns, such as early repolarization, which can also be associated with the risk of sudden cardiac death. Finally, we agree with Dr. Anselm on the importance of performing a challenge test with flecainide to rule out Brugada syndrome. Until the prognosis of patients presenting with Brugada phenocopy has been established, it is advisable to perform pharmacological challenge tests and, if appropriate, to induce ventricular arrhythmias by means of an electrophysiological study.