Pathogenetic mechanisms of COVID-19 (Corona Virus Disease 2019 — coronavirus infection 2019) development may manifest atypically in some patients with hereditary connective tissue diseases. A clinical description of the rupture of left ventricular (LV) wall aneurysm in a patient with Marfan syndrome after COVID-19 re-infection is presented. The patient was admitted with complaints of mixed dyspnea, dry cough, 38.2 °C body temperature. He suffered from focal myocarditis in 2022 (laboratory-confirmed COVID-19). The signs of bilateral infiltrative loci in the lungs were identified according to the chest computed tomography data. CT stage-3 (67% lung tissue lesion). A fatal outcome occurred in presence of acute heart and respiratory failure. Signs of viral interstitial pneumonia were revealed in autopsy study. The wall was moderately expanded on the side of the LV posterior wall with a transition to the lateral, loci with its impaired integrity were identified. Thus, in the patient with Marfan syndrome, SARS-CoV-2 re-infection was complicated by the development of severe viral interstitial pneumonia, diffuse dystrophic necrotic myocarditis and rupture of the LV wall aneurysm.