Myocardial thickening and isolated left ventricular abnormal trabeculation (ILVAT) have not been described in patients with Leber's hereditary optic neuropathy (LHON) before. Wolff-Parkinson-White syndrome, myocardial thickening and ILVAT were found by electrocardiogram, echocardiography and cardiac magnetic resonance imaging in a 48-year-old man with bilateral, severely reduced visual acuity since age 24 years, palpitations since age 43 years and lower limb muscle cramps since age 47 years. Because ILVAT is frequently associated with respiratory chain disorders, neurological investigations were initiated, revealing the primary LHON mutation G3460A in lymphocytic mitochondrial DNA. On the basis of the clinical and genetic data, LHON was diagnosed in the index patient, but also in the patient's brother who showed ILVAT as well. Wolff-Parkinson-White syndrome, myocardial thickening and ILVAT may be rare manifestations of LHON.