Systemic lupus erythematosus (SLE) is a prototypic systemic autoimmune disease that develops in genetically susceptible individuals in response to environmental factors. SLE and primary immunodeficiency disease (PID) share some clinical manifestations in that certain PIDs present with autoimmune phenomena. Patients with SLE become susceptible to infection via three pathways. First, SLE and PID share some genetic factors, such as complement and mannose-binding lectin genes, which predispose patients to infection. Second, patients with SLE have an inherently high risk of infection because of their intrinsic immunological abnormalities induced by SLE. Third, patients with SLE receiving immunosuppressive treatment are at high risk of infection. Further studies delineating the abnormalities related to both autoimmunity and immunodeficiency would be warranted to identify a new potential drug target for SLE.

Favipiravir, an antiviral agent, is undergoing clinical trials for treating novel coronavirus disease 2019 (COVID-19). Here, we report two cases of COVID-19 with favipiravir-induced fever. In both cases, pyrexia was observed following the administration of favipiravir despite improvements in symptoms of COVID-19. No other cause for fever was evident after careful physical examination and laboratory investigation. The fever subsided in both patients after the discontinuation of favipiravir. To the best of our knowledge, this is the first report of favipiravir-induced fever in COVID-19 patients.

Renal involvement is underestimated as an extramuscular manifestation of dermatomyositis (DM). Here, we describe a 67-year-old woman with anti-glycyl-transfer ribonucleic acid synthetase (anti-EJ) antibody and anti-ribonucleoprotein antibody-positive DM complicated by systemic sclerosis, who developed nephrotic syndrome concurrently with the exacerbation of DM, as indicated by incremental serum creatine kinase levels, high-intensity lesions on muscle magnetic resonance imaging, and active interstitial pneumonitis on chest computed tomography. Renal biopsy revealed the presence of immune-deposition in the glomerulus by immunofluorescence. To our knowledge, this is the first report describing the coexistence of anti-EJ antibody-positive DM and nephrotic syndrome. More reports of similar cases are warranted to substantiate the association.