Primary (pIgAN), secondary IgA nephropathy (sIgAN), and IgA-associated nephropathy can be distinguished. While pIgAN has been thoroughly studied, information about the etiology of sIgAN remains scarce. As concerns sIgAN, several studies suggest that different etiologic factors play a role and ultimately lead to a pathophysiologic process similar to that of pIgAN. In this article, we review a vast number of cases in order to determine the novel putative underlying diseases of sIgAN. Moreover, updates on the common pathophysiology of primary disorders and sIgAN are presented. We identified liver, gastrointestinal, oncological, dermatological, autoimmune, and respiratory diseases, as well as infectious, iatrogenic, and environmental factors, as triggers of sIgAN. As novel biological therapies for listed underlying diseases emerge, we suggest implementing drug-induced sIgAN as a new significant category. Clinicians should acknowledge the possibility of sIgAN progression in patients treated with TNF-α inhibitors, IL-12/IL-23-inhibitors, immune checkpoint inhibitors, CTLA-4, oral anticoagulants, thioureylene derivatives, and anti-vascular endothelial growth factor drugs.

Outdoor sports are associated with increased exposure to ultraviolet radiation, which may result in sunburn, solar damage, and skin cancers. Water and winter sports create additional adverse conditions, such as washing away sunscreen by water and reflection of UV rays by the water and snow. Sweating-increased skin photosensitivity and activity-induced immunosuppression are associated with a greater risk of developing skin cancers. In this review, we focus on a group of athletes and sports participants and analyze 62 articles concerning sun exposure during outdoor sports, the risk of developing skin cancer, and knowledge and behavior regarding photoprotection methods. Various practices have been linked to an increased risk of developing basal cell carcinoma (BCC), squamous cell carcinoma (SCC), malignant melanoma (MM), or UV-induced skin damage. Water sports and mountaineering increase the risk of BCC. Surfing and swimming are risk factors for SCC. Melanoma is more common in swimmers, surfers, and marathon runners. Photoprotection behaviors can reduce potential skin damage and skin cancers. Athletes’ knowledge about the risk of malignant lesions was satisfactory, but despite the risks, outdoor sports participants seem not to protect themselves from the sun adequately.

Review question / Objective: To determine the novel putative underlying diseases and to identify etiologic factors of secondary IgA nephropathy. Condition being studied: Primary (pIgAN), secondary IgA nephropathy (sIgAN), and INPLASY 1 International Platform of Registered Systematic Review and Meta-analysis Protocols