So far, studies have shown that children appear to represent 2.4% of reported cases of COVID-19. The overall severity of COVID-19 in children was reported to be significantly milder than in adults (11). As COVID-19 continues to spread, there is growing evidence that children may be vulnerable to another rare or even a serious complication of disease. They might be experienced hospitalization with the risk of superinfection and bacterial colonization (12). Case reports have appeared describing the pediatric patients with unusual presentations of Kawasaki s disease, toxic shock syndrome, acute abdominal conditions, and encephalopathy, macrophage activation syndrome, along with other reports of patients with fever, elevated inflammatory markers, and multisystem involvement as a new entity called childhood multisystem inflammatory syndrome (13).
However, reports of viral arthritis in this pandemics are lacking in both pediatric and adult patients. Albeit, the viral infections are a well-recognized cause of acute arthralgia and arthritis with a large number of causative agents. The diagnosis of this condition can be difficult for clinicians to confirm. In addition, to clinical features that point the clinicians to a specific virus, serological testing may be requested based on both clinical and epidemiological data. Accurate data regarding the incidence and prevalence of virally induced arthritis are lacking. Studies have suggested a viral etiology in about 1% of cases of acute arthritis. Worldwide, Parvovirus B-19, Hepatitis-B and C. HIV and the alpha viruses are among the most important causes of virally induced arthritis (14).
The pathogenesis of post viral arthritis is complex, because they often do not meet the classical definition criteria of reactive arthritis, and there being some viral infections (rubella, varicella zoster, herpes simplex virus, cytomegal virus, etc.) during which the virus can be isolated in synovial fluid (15). With other viral infections (hepatitis-B, adenovirus type-7) in synovial fluid antigen-antibody immune complexes were isolated, highlighting a possible role of these in the pathogenesis of virally induced arthritis (15-17). Generally, post infectious arthritis involves the lower limb joints especially ankles and knees and can cause limping occurrence (18, 19). However, it is important to maintain that in about 50% of cases, the etiologic agent cannot be isolated, and in 25% of children with post infectious arthritis, the infection is asymptomatic in history (15).
Our patients had no history of falling or other traumatic process. Also, both of them had no evidence of serious and life threatening condition like septic arthritis, osteomyelitis, malignancies and other causes. Both of them had a preliminary mild symptoms of upper respiratory infection including fever and cough about seven days earlier to limp. The first case referred with a prolonged duration of limp for three weeks, and the second one had the additional polyartheralgia in this period. The IgM and IgG levels against nCoV-2 were significantly higher than normal first and after 1 week, respectively. Although, his parents refused to do the nasopharyngeal sampling; due to latency visit and evaluation from precede symptoms, the molecular evaluation was of little value. The patient was considered as a reactive arthritis and gave a good response to the NSAID treatment, and of course, with 40 days follow up, he was completely fine and had no other problem. In the second patient, the results were positive for both serological and molecular tests. In addition, in her mother, has a positive PCR test and experienced mild symptoms. These two patients are symbols of the coronavirus arthrogenicity; what has been seen a lot with other viral infections, but so far has not been reported after nCoV-2 infection. At this days, we see some other cases of coronavirus related arthralgia, which suggesting more consideration to pediatricians. Further reports will help clarify the corona virus arthrogenicity.