Here, we present a longitudinal analysis of two patients who recovered from COVID-19 more than 8 months prior but showed persistent serological detection of anti-SARS-CoV-2 IgM. We still do not know the exact reason for this prolonged persistence of IgM in these patients. To our knowledge, these are the first reports of IgM persistence in the context of SARS-CoV-2 infection and point to the need for no longer using IgM as a diagnostic criterion for acute or recent COVID-19. One should opt for gold standard molecular methodologies due to their high sensitivity and specificity.

Hepatitis C virus (HCV) infection is a serious public health concern due to its high prevalence and mortality rate. In chronic infection, HCV may induce autoimmune responses through the production of autoantibodies, including anti-nuclear antibodies (ANA). We assessed the presence of ANA by indirect immunofluorescence using HEp-2 cells in 89 patients with chronic hepatitis C. We also collected data on epidemiological variables; clinical characteristics; and biochemical, hematological, molecular and histopathological information from the patients to assess the impact of the presence of ANA in those patients. The prevalence of ANA in the patients was 20.2%, which was significantly higher than that found in healthy controls (2%). However, there was no association of this marker with epidemiological, clinical-laboratory, molecular or histopathological characteristics of hepatitis C, although a slightly higher prevalence of ANA was detected in women and in patients infected with subgenotype 1a. In a specific analysis, chronic HCV patients with the “rods and rings” cytoplasmic pattern had higher degrees of hepatic fibrosis than did ANA-negative patients. The results suggest a greater predisposition to the presence of ANA in patients with HCV, which may be associated with a worse prognosis, especially in the presence of the “rods and rings” cytoplasmic pattern.