Approximately 5–15% of children develop post-COVID-19 syndrome after SARS-CoV-2 infection, which manifests itself with various pathological symptoms for more than 12 weeks. Cardiovascular symptoms range from serious myocardial inflammation, manifestations of essential hypertension to signs of autonomic dysfunction with a tendency to hypersympathicotonia, which negatively affects the quality of life of children. We report a case of subacute myocarditis in a patient with long-COVID after a low-symptomatic acute disease. This case illustrates high clinical significance of timely diagnosis of long-COVID using gadolinium-enhanced magnetic resonance imaging, which was performed in our country for the first time in pediatric practice. We developed criteria for early diagnosis of autonomic dysfunction specific for children and adolescents. We also developed treatment recommendations, including behavioral therapy, drug, and non-drug treatments. Key words: long-COVID, autonomic dysfunction, hypersympathicotonia, myocarditis, behavioral therapy, non-drug treatment

Neuroendocrine cell hyperplasia of infancy (NEHI) is an interstitial lung disease of unknown etiology that develops in infancy and manifests as persistent tachypnea syndrome. A highly informative scale for the clinical diagnosis of NEHI and CT of the lungs is used to diagnos the disease. The presence of a typical CT picture allows the diagnosis of NEHI to be made. We present a clinical case of a patient diagnosed on the basis of the scale of clinical diagnostics and a typical CT picture of NEHI, complicated by protein-energy insufficiency, chronic respiratory failure of II degree, who is on long-term home oxygen therapy.