Reactive arthritis (ReA) is defined as arthritis that arises after infection, where pathogens cannot grow in the affected joints. Formerly, the clinical triad of postinfectious arthritis, urethritis, and conjunctivitis was called Reiter's syndrome; however, these clinical signs only represented a subset of patients with ReA. Due to the great diversity of its manifestations, its diagnosis is a challenge and can be overlooked in clinical practice. Additionally, it is associated with a variety of extra-articular manifestations that may be present either in the acute or chronic phase of the disease. Despite the cardinal clinical presentation characteristics of ReA, no case has been described in the literature that is diagnosed by the presence of classic extraarticular manifestations without objective joint involvement after COVID-19 infection. This report describes the case of a female patient in her third decade of life with an unusual presentation of ReA and focuses on her extra-articular manifestations.

In the current medical literature, there is increasing evidence for the involvement of the interleukin (IL)-17/23 axis and the potential role of Th17 cells in the pathogenesis of lupus nephritis. Knowledge about the interaction of these immunological pathways in the development of autoimmune diseases has led to the identification of new therapeutic strategies aimed at blocking them. For this reason, the main objective of this review focuses on knowing the recent evidence of the different anti-IL-17/23 treatment strategies in lupus nephritis and their future perspectives. A non-systematic narrative review of the literature was carried out following the objective of having the most representative information on the different anti-IL-17/23 drugs available together with the description of the pathophysiological mechanisms of this pathway involved in systemic lupus erythematosus and lupus nephritis. Despite the great existing theoretical foundation, today few clinical studies support the use of these therapies in both contexts. Nevertheless, the publication of research with a better methodology is expected to approve the indication of some of these drugs in lupus nephritis. However, the clinical response seen with ustekinumab and secukinumab in clinical studies and case reports published to date has been encouraging.

Systemic lupus erythematosus is a multisystemic disease that usually involves the urinary tract, often in the form of lupus nephritis. However, another form of compromise of this system is lupus cystitis, which, despite being an unusual condition, turns out to be a challenging diagnosis due to the spectrum of nonspecific abdominal and urinary symptoms. Although the exact pathophysiological mechanism of bladder inflammation remains to be established, the role of small vessel vasculitis measured by immune complexes continues to be supported as a central axis for considering possible therapeutic targets. Additionally, there are no clinical studies that dictate a guideline regarding its treatment, however, the evidence from most cases described in the literature suggests the initiation of pulses of methylprednisolone and cyclophosphamide in treatment regimens similar to those of lupus nephritis. Despite its low prevalence, obstructive complications and kidney damage can lead to increased morbidity and mortality.

Reactive arthritis is defined as arthritis that arises after infection, where pathogens cannot grow in the affected joints. Although the human immunodeficiency virus and severe acute respiratory syndrome coronavirus 2 are not among the most commonly implicated pathogens, there is growing evidence that they have major implications in the genesis of reactive arthritis. However, there are no described cases of coinfection of both entities that cause reactive arthritis at the same time, and the alterations involved in the immune system that could cause the change of certain clinical characteristics to more severe forms of the disease are unknown. The following describes the case of a male patient in his third decade of life who has an unusual and severe presentation of reactive arthritis associated with coinfection by COVID-19 and the human immunodeficiency virus.