Lymphatic hypoplastic diathesis (LDH) is one of the constitutional and anatomical anomalies found in children, characterized by hyperplasia of lymphatic tissues, immunological dysfunction and high susceptibility to infectious and allergic diseases. In this case, an increase in the thymus, lymph nodes and adenoid tissues, a violation of the humoral and cellular immune response are observed. Patients may experience respiratory infections, allergic reactions and functional cardiovascular changes - sinus tachycardia, bradycardia and extrasystoles. Cardiac arrhythmias are mainly associated with vegetative dysfunction and a dysimmune state, and are not associated with organic pathologies of the heart. Lymphatic hypoplastic diathesis is one of the urgent problems that need to be studied in clinical pediatrics, pediatric immunology and cardiology, and its early diagnosis and comprehensive control are of great importance in ensuring resistance to infections and preventing complications. Purpose.