Novel Use of Mavacamten in RAF1-Associated Noonan Syndrome With Hypertrophic Cardiomyopathy.

BACKGROUND: Mavacamten is a first-in class allosteric inhibitor of cardiac myosin that is shown to reduce left ventricular outflow tract obstruction and improves symptoms in obstructive hypertrophic cardiomyopathy (HCM). However, there have been limited studies of the use of mavacamten in nonsarcomeric forms of HCM, such as Noonan syndrome. CASE SUMMARY: This case report describes therapeutic benefit with mavacamten in a 26-year-old man with RAF1-associated Noonan syndrome and previous septal myectomy. DISCUSSION: This case represents one of the first reports of mavacamten use in RAF1-associated Noonan syndrome, a nonsarcomeric form of HCM, in a patient with recurrent obstruction after early septal myectomy. Treatment was associated with progressive reduction in left ventricular outflow tract gradients and symptomatic improvement, supporting myosin inhibition as a potential therapeutic strategy in syndromic HCM. TAKE-HOME MESSAGE: Mavacamten may be an effective treatment for obstructive HCM from RAF1-associated Noonan syndrome.