The classic presentation (in 40-50% of the cases) is episodic frank hematuria which usually starts within a day or two of a non-specific upper respiratory tract infection (hence synpharyngitic) as opposed to post-streptococcal glomerulonephritis which occurs some time (weeks) after initial infection. Less commonly gastrointestinal or urinary infection can be the inciting agent. All of these infections have in common the activation of mucosal defenses and hence IgA antibody production. Iodinated contrast media
Kidney disease induced by iodinated contrast media (ICM) is called CIN (= contrast induced nephropathy) or contrast-induced AKI (= acute kidney injury). Currently, the underlying mechanisms are unclear. But there is a body of evidence that several factors including apoptosis-induction seem to play a role. Lithium
Lithium, a medication commonly used to treat bipolar disorder and schizoaffective disorders, can cause nephrogenic diabetes insipidus; its long-term use can lead to nephropathy. Lupus
Despite expensive treatments, lupus nephritis remains a major cause of morbidity and mortality in people with relapsing or refractory lupus nephritis. Xanthine oxidase deficiency
Another possible cause of Kidney disease is due to decreased function of xanthine oxidase in the purine degradation pathway. Xanthine oxidase will degrade hypoxanthine to xanthine and then to uric acid. Xanthine is not very soluble in water; therefore, an increase in xanthine forms crystals (which can lead to kidney stones) and result in damage to the kidney. Xanthine oxidase inhibitors, like allopurinol, can cause nephropathy. Polycystic disease of the kidneys
Additional possible cause of nephropathy is due to the formation of cysts or pockets containing fluid within the kidneys.
They go on to say "Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic disease, affecting a half million Americans. The clinical phenotype can result from at least two different gene defects. One gene that can cause ADPKD has been located on the short arm of chromosome 16." The same article also goes on to say that millions of Americans are effected by this disease and is very common. Long COVID and Kidney Disease
Yende & Parikh 2021 talk about the effects that COVID can have on a person that has a pre-existing health issue regarding kidney diseases. "frailty, chronic diseases, disability and immunodeficiency are at increased risk of kidney disease and progression to kidney failure, and infection with SARS-CoV-2 can further increase this risk” (Long COVID and Kidney Disease, 2021). Diet
Higher dietary intake of animal protein, animal fat, and cholesterol may increase risk for microalbuminuria, a sign of kidney function decline, and generally, diets higher in fruits, vegetables, and whole grains but lower in meat and sweets may be protective against kidney function decline. This may be because sources of animal protein, animal fat, and cholesterol, and sweets are more acid-producing, while fruits, vegetables, legumes, and whole grains are more base-producing. IgA nephropathy
IgA nephropathy is the most common glomerulonephritis throughout the world  Primary IgA nephropathy is characterized by deposition of the IgA antibody in the glomerulus.