Abstract We report two cases of overlap syndrome between IgG4-related disease (IgG4-RD) and systemic lupus erythematosus (SLE), encountered in distinct rheumatology centers in France and Romania. The co-occurrence of SLE and IgG4-RD is rare, and both cases highlight the intersection of these autoimmune conditions. The overlapping features of both diseases present a diagnostic challenge but offer an opportunity for a greater understanding of the pathophysiological interactions between IgG4-RD and SLE. Clinicians must be vigilant in distinguishing between these entities, as they carry different therapeutic implications.
Baciu et al. (Wed,) studied this question.