So far, left ventricular hypertrabeculation (LVHT) has been described to occur only sporadically. In a 49-year-old man with Leber's hereditary optic neuropathy (LHON) due to the primary LHON mutation G3460A, arterial hypertension was reported since 2000 and palpitations since 1995. ECG revealed Wolff-Parkinson-White syndrome. Transthoracic echocardiography and cardiac MRI showed myocardial thickening and LVHT. Pindolol markedly improved the cardiac abnormalities. Surprisingly, LVHT was also found in the 50-year-old brother of the index patient who also had LHON and also carried the G3460A mtDNA mutation. This brother also had Wolff-Parkinson-White syndrome and myocardial thickening, but without hypertension. It is concluded that LVHT, previously described to occur only sporadically, may be hereditary in single cases.