CD40LG and respiratory tract infectious disorder: Initially, COVID-19 was diagnosed in 2/4 (50%) cases: two children had signs of respiratory infection (rhinitis and cough); one patient was SARS-CoV-2 positive based on an RT-PCR test from a nasopharyngeal swab, accompanied by a positive IgG antibody, and one patient had both IgM and IgG antibodies against SARS-CoV-2.