Four-day fever at 39.5°C, vomiting (three days), no improvement, diarrhea (two days), COVID-19, IgG positive and IgM negative, physical examination: conjunctival infection exanthematous lesions/erythema on palm and plantar level, red mouth mucosa, lab results: high WBC (22.21), high neutrophils (91%), low hemoglobin (10.1), low hematocrit (30.1%), normal platelets (150), normal monocytes (4.3%), and low lymphocytes (4.1%). Here, CD40LG is linked to Erythema.