Membranous nephropathy (MN) is a disease with an etiology and pathogenesis that are still not fully understood, and it represents a great challenge. It is characterized by a variable course, spontaneous remissions and relapses. The inability to rely entirely on antibodies and the continuous threat of a malignant disease make the differentiation of MN types extremely difficult. Data of twelve patients with membranous nephropathy, ranging in age between 28 and 67 years, are presented; in total, seven men and five women were observed for a period of 2 to 10 years. In all patients, the diagnosis was confirmed through kidney biopsy and laboratory tests, including immunological, histopathological, and immunohistochemical tests. Histopathological and immunohistochemical tests were applied on available material from the thyroid gland in two patients and the gallbladder in two patients with MN. Data of 102 patients with MN and their comorbidities are evaluated in order to establish correlations. These and other data are used to build a hypothetical pathogenetic model that explains the etiology and the likely pattern of disease occurrence. We found a connection between chronic cholecystitis, thyroiditis, hepatitis, and other diseases in the occurrence of MN and disease course. From our practice and cases, we drew the conclusion that chronic inflammation in sites that express PLA2R leads to the formation of antibodies against PLA2R. These antibodies occur as a preformed immune complex or separately and are deposited in the subepithelial space, leading to MN appearance.

Rhabdomyolysis is one of the leading causes of acute kidney injury (AKI) and is infrequently associated with chronic kidney disease (CKD). CKD appears in diabetes mellitus and arterial hypertension, as a result of other systemic diseases and glomerulonephritis. In this study, we present two cases (one with CKD and one with AKI) that are caused by a genetic defect. A genetic examination was performed in both patients, proving that the patient with CKD has a genetic defect in the RYR1 gene, which is observed in patients with malignant hyperthermia. Meanwhile, the patient with AKI has a homozygous pathogenic variant in SLC2A9, which is associated with urinary urate wasting and is characterized by asymptomatic hypouricemia and AKI after exercise. The first case is chronic rhabdomyolysis, as the patient is an athlete and performs heavy daily exercise. The second case is AKI without prior kidney damage or symptoms. Both patients did not undergo a kidney biopsy. In the first case, changes in daily routine without extreme physical exercise led to the recovery of normal kidney function. The second patient recovered from AKI without sequelae. These two cases are an example of “thinking outside the box” with respect to how genetic diseases and defects can cause kidney damage, both chronic and acute.

Membranous nephropathy is a disease that has been well documented, yet its etiopathogenesis has not been fully clarified and the distinction between its primary and secondary forms has not been completely categorized. The discovery of new antigens and antibodies reveals different percentages of positivity in secondary membranous nephropathy, which is a cause of great confusion and ambiguity not only in diagnosis but also in the choice of a therapeutic approach. The aim of this review is to summarize the literature on newly discovered antigens and antibodies, and to propose a pathogenetic model based on the role of the complement system and its activation pathways. In this model, antigens are categorized based on the type of immunoglobulin deposits and the putative complement pathways that they activate, which can help to differentiate primary from secondary membranous nephropathy. The model also reflects how the deposition of foreign antigens in the basement membrane can activate both the lectin and classical complement pathways, which may explain why positive antibodies are observed in both primary and secondary forms of membranous nephropathy.