A rare deleterious case of concomitant renal disease associated with IgG4-associated systemic disease

In IgG4-associated disease, several organs and tissues are often affected, especially kidney tissue, and is characterized by interstitial nephritis, obstructive nephropathy, and in rare cases glomerulopathy (including membra[1]nous nephropathy). IgG4-associated disease was isolated as an independent nosological form in 2003, when patients with type 1 autoimmune pancreatitis were found signs of systemic damage (involvement of the biliary tract, salivary glands, retroperitoneal space), and in 2012 the first international nomenclature of the disease was proposed. The clinical manifestations of IgG4-associated disease are nonspecific and diverse, which determines the difficulties of differential diagnosis, including infections and tumors, and increases the period from the onset of the disease to diagnosis to an average of 2 years. IgG4-associated disease is more likely to develop in middle age and old age. The prevalence of the disease is higher among men than among women. Thus, autoimmune pancreatitis type 1, retroperitoneal fibrosis and tubulointerstitial nephritis are more common in men, and sialoadenitis, dacryoadenitis and thyroiditis are more common in women. In this article, we present a clinical case of IgG4-associated systemic disease with a combined lesion of the tubulo-interstitial and glomerular compartments of kidney tissue with nephrotic syndrome as the only initial manifestation. The combination of IgG4-tubulo-interstitial nephritis with membranous nephropathy is an ex[1]tremely rare pathology. Nephrobiopsy was crucial in the diagnosis of this condition, which allowed the patient to be prescribed proper and timely treatment.