FOCAL SEGMENTAL GLOMERULOSCLEROSIS (FSGS)
Focal Segmental Glomerulosclerosis (FSGS) is a type of Glomerular Disease, one of many diseases that affect kidney function by attacking the glomeruli, the tiny units within the kidney where blood is cleaned. Glomerulosclerosis (gloh-MAIR-yoo-loh-skleh-ROH-sis) describes the scarring or hardening of the tiny blood vessels within the kidney.
Glomerulonephritis refers to diseases that damage the filters or glomeruli of the kidney. Glomeruli are tiny structures composed of blood vessels that are responsible for filtering the blood of harmful or unnecessary substances. There are a million glomerular filters within each kidney. In glomerulonephritis, inflammation of some or all of the glomerular filters reduces their ability to clear these substances out of the bloodstream. The damage also allows protein to leak through the filters into the urine and this is referred to as proteinuria or albuminuria. Red blood cells may also leak through the filters into the urine. When very large amounts of protein are lost in the urine, it is often called nephrotic syndrome.

FOCAL SEGMENTAL GLOMERULOSCLEROSIS (FSGS)
Focal segmental glomerulosclerosis or FSGS is a disease that causes urinary loss of protein and eventual scarring of the glomerular filters of the kidney. The terms focal and segmental refers to the pattern of damage in the kidney as seen under a microscope. Focal means that some of the glomeruli are scarred while others are normal. Segmental means that only a part of an individual glomerulus is damaged.

FSGS can develop as an isolated kidney disease (referred to as primary FSGS). In these cases, the cause of the disease is unknown. FSGS can also be due to other causes (referred to as secondary FSGS). In some of these cases, the disease may due to being born with too few glomeruli (ie. being born with a single kidney) or it may be associated with conditions that overwork the filters of the kidney such as with massive obesity. However, a wide variety of factors including infections, medications/toxins, chronic systemic diseases and other chronic kidney diseases can also result in the same pattern of disease. Rarely, the disease is inherited and much research is ongoing at the Glomerular Center at Columbia to understand the genes that may be responsible for the disease.

Primary FSGS affects individuals of all ages. It is an important cause of kidney problems in children. In adults, it is also increasingly seen. It occurs more frequently in black individuals compared to whites and is more frequent in males.

WHAT ARE THE KIDNEYS AND WHAT DO THEY DO?
The two kidneys are bean-shaped organs located near the middle of the back, just below the rib cage to the left and right of the spine. Each about the size of a fist, these organs act as sophisticated filters for the body. They process about 400 quarts of blood a day to sift out about 2 quarts of waste products and extra water that eventually leave the body as urine.

Blood enters the kidneys through arteries that branch inside the kidneys into tiny clusters of looping blood vessels. Each cluster is called a glomerulus, which comes from the Greek word meaning filter. The plural form of the word is glomeruli. There are approximately 1 million glomeruli, or filters, in each kidney. The glomerulus is attached to the opening of a small fluid-collecting tube called a tubule. Blood is filtered in the glomerulus, and extra water and wastes pass into the tubule and become urine. Eventually, the urine drains from the kidneys into the bladder through larger tubes called ureters.

Each glomerulus-and-tubule unit is called a nephron. Each kidney is composed of about 1 million nephrons. In healthy nephrons, the glomerular membrane that separates the blood vessel from the tubule allows waste products and extra water to pass into the tubule while keeping blood cells and protein in the bloodstream.

Source: National Kidney and Urologic Diseases Information Clearinghouse
3 Information Way
Bethesda, MD 20892-3580
Email: nkudic@info.niddk.nih.gov
The National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC) is a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The NIDDK is part of the National Institutes of Health under the U.S. Department of Health and Human Services. Established in 1987, the clearinghouse provides information about diseases of the kidneys and urologic system to people with kidney and urologic disorders and to their families, health care professionals, and the public. NKUDIC answers inquiries, develops and distributes publications, and works closely with professional and patient organizations and Government agencies to coordinate resources about kidney and urologic diseases. Publications produced by the clearinghouse are carefully reviewed by both NIDDK scientists and outside experts.
NIH Publication No. 03-4358
March 2003