Unfortunately, medical terminology includes many long words that are difficult to pronounce (and spell), and “glomerulonephritis” is one of them.

But it’s an important type of kidney disease, so we will discuss this group of disorders in this edition of the Kidney Corner. It means “inflammation of the filtering parts of the kidney” and is sometimes called more simply “nephritis.” An older term is “Bright’s disease.” Here, we will abbreviate it to “GN.”

Since the kidney functions as a filter, it makes sense that the filter can get clogged up by substances in the blood that then prevent the filter from working correctly. This is a gross oversimplification of the mechanism of GN, but is a good way to conceptualize the problem.

The circulating substances that most commonly cause this inflammation are immunoglobulins, the proteins in the blood that the body makes to fight infections. If immunoglobulin levels are too high, or if they have a disordered structure, they can result in GN.

The result can be protein loss from the kidney, high blood pressure and sometimes kidney failure.

Some of the most common causes of GN are infections. The best-known example is Streptococcus, commonly known as “strep,” which can cause sore throats. Usually, a “strep throat” will get better on its own with no consequences.

In rare cases, however, the immunoglobulins made by the body to combat the strep infection can cause severe GN. This may present as blood in the urine and sometimes as kidney failure. This problem is most commonly seen in young people.

Fortunately, Streptococcal GN usually gets better after a few weeks.

Another common cause of GN, especially in Native American patients, is a problem called “IgA nephritis.” This may also follow infections of various types or can occur without any underlying cause. It varies from being a minor problem without symptoms, which causes no clinical consequences, to a severe disease potentially causing kidney failure.

There are effective medicines for IgA nephropathy, but since they have the potential for significant side effects, they are usually reserved for the most severe cases that threaten the survival of the kidneys.

IgA may cause blood in the urine, especially after infections. Although this appears alarming, it usually subsides without damage; much more dangerous is protein in the urine, which usually can only be detected by chemical testing of the urine.

There are many more types of GN. Each is treated differently, and a definitive diagnosis usually requires a kidney biopsy in which a piece of kidney tissue is removed using a needle. For many types — though we know much about how the disease behaves and what is needed to treat it — we often don’t know the cause.

Nevertheless, treatment can be very successful and can protect the kidney from unnecessary damage.