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Polymyositis is a rarely reported complication of COVID-19 illness, especially in children. Molecular mimicry may be a cause of hyperactivated autoimmunity, leading to various clinical manifestations, including myopathies. Symptoms vary from mild muscle weakness to severe rhabdomyolysis. We review the literature on post-COVID myositis and report a case of severe polymyositis in a 7-year-old boy, following undefined viral infection 3 weeks before the onset of muscle pain. Patient's condition deteriorated from physical activity-associated pain in the lower limbs to severe muscle weakness leading to dysphagia and mechanical ventilation. As antibodies against SARS-CoV-2 were detected and other possible conditions causing myositis were excluded, the diagnosis of post-COVID polymyositis was considered as the most likely. The patient was treated with high doses of methylprednisolone and cyclophosphamide, resulting in improvement. Although COVID-19 is becoming a seasonal disease, the infection itself and post-viral disorders, such as polymyositis, are still of great interest and require better investigation to ensure appropriate management for each individual. Our experience suggests that aggressive immunosuppressive therapy might be a solution for severe post-COVID-related diseases. This literature review is provided in addition to the case report presented at the 29th European Paediatric Rheumatology Congress; the abstract is available online in the Proceedings of the 29th European Paediatric Rheumatology Congress. [ABSTRACT FROM AUTHOR]

This report describes clinical features and tactics of treatment of atrial tachyarrhythmias in infancy. Electrophysiologic study was performed in all 20 infants (2 weeks - 12 months old) in order to determine the mechanism of arrhythmia and to predict the clinical efficacy of management. Reciprocating mechanism was revealed in 12 infants. Atrial flutter was diagnosed for 10 infants among whom only 2 patients were older than two months. Six infants were found to have flutter conduction with a rate of 1:1. Four infants had congestive heart failure, 3 of them with a structurally normal heart. Half of the infants with atrial flutter needed long-term antiarrhythmic therapy. Electrotherapy for termination of atrial flutter was effective in all of them. Automatic atrial tachycardia in eight infants presented no major problems unless it became incessant and resistant to pharmacological treatment. The average tachycardia rate reached 171±7 beats/mm. Atrial reciprocating tachycardia usually affects patients with diseased myocardium. [ABSTRACT FROM AUTHOR]

Unlabelled: Radiofrequency ablation of the slow pathway is an effective method of treatment in children with atrioventricular nodal reentrant tachycardia. The aim of our study was to evaluate anterograde conduction properties in children before and after radiofrequency ablation of the slow pathway and to determine the efficacy and safety of this method., Material and Methods: Noninvasive transesophageal electrophysiological examination was performed in 30 patients at the follow-up period (mean duration, 3.24 years) after radiofrequency ablation of the slow pathway., Results: The slow pathway function was observed in 13 patients one day after ablation, in 26 patients during the follow-up period, and in 28 patients after administration of atropine sulfate. Atrioventricular node conduction was significantly decreased the following day after ablation and at the follow-up versus the preablation (165.2 [30.2] bmp and 146.3 [28.5] bpm versus 190.9 [31.4] bpm; P<0.001). The atrioventricular node effective refractory period prolonged significantly the following day after ablation and at the follow-up versus the preablation (319.3 [55.3] ms and 351.0 [82.1] ms versus 248.3 [36.6] ms; P<0.001). Effective refractory period of the fast pathway prolonged significantly as compared with the preablation (from 408.0 [60.4] ms to 481.2 [132.9] ms; P=0.005). The prolongation of effective refractory period of the slow pathway was more significant than effective refractory period of the fast pathway at the follow-up (P<0.001). Two late recurrences occurred; one patient had atrial tachycardia., Conclusion: Children with atrioventricular nodal reentrant tachycardia can be effectively and safety cured by ablative therapy. The end-point during slow pathway ablation should be the abolition of tachycardia with preservation of dual atrioventricular nodal physiology.

Unlabelled: Idiopathic ventricular tachycardia is a rare condition, and there is a lack of clear guidelines for the necessity and indications for prophylactic antiarrhythmic or curative treatment. The aim of this study was to review the clinical picture of idiopathic ventricular tachycardia and evaluate the efficacy and safety of radiofrequency ablation therapy in children., Material and Methods: The subjects of this study were 16 children with idiopathic ventricular tachycardia. The mean age at onset of idiopathic ventricular tachycardia was 12 years. All patients underwent electrophysiological examination. Nonfluoroscopic mapping technology (Carto) was used in one case. Radiofrequency ablation was performed in all children (mean duration of follow-up was 46 months)., Results: Six children with idiopathic ventricular tachycardia were free of symptoms. Palpitation was the only complain in four patients, and six patients presented with symptoms of circulatory disorder (the tendency of the higher rate of ventricular tachycardia and more premature contractions and episodes of ventricular tachycardia in one day were noticed in five of them). All children after radiofrequency ablation were alive, and only one complication (complete right bundle branch block) occurred. Success at last follow-up included five children with left and six with right idiopathic ventricular tachycardia., Conclusions: Catheter ablation seems a promising therapeutic option with the outlook possible of the idiopathic ventricular tachycardia in children. It is safe enough and should be considered as the therapy of choice even in children without of symptoms if they wish to live active social and physical life.

Unlabelled: The aim of our study was to estimate etiology, most common clinical findings, the course and peculiarities of treatment in children to whom Henoch-Schönlein purpura was diagnosed during 1996-2002 at Clinic of Children's Diseases of Kaunas University of Medicine Hospital., Methods: The Henoch-Schönlein purpura diagnosis was based on the association of non-trombocytopenic purpura, arthritis and abdominal pain in 45 children, mostly at preschool age. Routine laboratory blood tests usually were normal. Serum level of imunoglobulin A (Ig A), complement 3, 4 (C(3), C(4)), antineutrophil cytoplasm antibodies were measured for some patients. Urinary analyses were performed for all patients in order to assess nephritis., Results: In 1/3 (33.3%) of children Henoch-Schönlein purpura was preceded by an upper respiratory tract infection. The most common clinical signs were: non-trombocytopenic purpura -100%, subcutaneous edema - 53%, arthritis of large joints - 64%, gastrointestinal symptoms (pain, diarrhea with bleeding) - 37.5%. The incidence of renal involvement was 13.3%, but usually not at the onset of the disease. Relapses were often, and they had tendency to repeat in 1-2 week periods. Late relapses were absent. Treatment of Henoch-Schönlein purpura was symptomic. Nonsteroidal anti-inflammatory drugs which are helpful in joint pain, were prescribed for 33.3% patients. Steroids which reduce abdominal pain, melena, massive hemorrhage, nephritic symptoms, were given for 28.8% patients., Conclusions: Non-trombocytopenic purpura, arthritis and colic abdominal pain, classic triad of Henoch-Schönlein purpura that occurs in early stage of the disease, were most common. Renal involvement had tendency occur later. Nonsteroidal anti-inflammatory drugs were prescribed for patients with arthritis; prednisone reduced gastrointestinal, nephritic symptoms. Relapses were often.