LEOPARD syndrome with accelerated idioventricular rhythm and systolic anterior motion of the posterior mitral leaflet: a case report.

BACKGROUND: PTPN11 is ubiquitously expressed and has a variety of phenotypes even in a single heart. We examined LEOPARD syndrome (LS) in a patient with PTPN11 variants through pathological, electrophysiological, and anatomical studies.

CASE SUMMARY: A 49-year-old man with no previous medical history was brought to our emergency department because of syncope. An electrocardiogram (ECG) revealed alternating bundle branch block, and echocardiography revealed hypertrophic cardiomyopathy-like morphology with systolic anterior motion of the posterior mitral valve. Atrioventricular block, left ventricular outflow tract (LVOT) obstruction, and ventricular tachycardia were considered the differential diagnoses; however, the treatment plan was difficult to determine. An electrophysiological study revealed the cause of the ECG abnormality to be accelerated idioventricular rhythm, and the programmed ventricular stimulation was negative. Genetic testing revealed LS with PTPN11 variant, which was speculated to be the cause of these various unique cardiac features. The cause of syncope was considered to be exacerbation of LVOT obstruction due to dehydration, and the patient was treated with oral beta-blockers. Implantable loop recorder observation for 1 year revealed no arrhythmia causing syncope, and an implantable cardioverter-defibrillator and pacemaker were deemed unnecessary for primary prevention of syncope. During 2.5 years of follow-up, the LVOT peak velocity fluctuated between 2.5 and 3.5 m/s, but the patient remained stable with no recurrent syncope.

CONCLUSION: We confirmed that LS is distinct from other cardiomyopathies using characterization, physiological, electrophysiological, and pathological examinations. Evidence supporting a specific treatment strategy for LS is limited, and understanding the pathogenesis may help establish effective treatment strategies.