Focal sclerosis most commonly refers to Focal Segmental Glomerulosclerosis (FSGS), a kidney disease. FSGS involves scarring of the kidney’s tiny filtering units, called glomeruli, which clean the blood. This condition impairs the kidney’s ability to filter waste and retain proteins, leading to various health complications.
What is Focal Segmental Glomerulosclerosis?
FSGS is a kidney disorder where scar tissue develops in the glomeruli, the kidney’s filtering units. The term “focal” indicates that only some glomeruli are affected by scarring, while others remain undamaged. “Segmental” means that within an affected glomerulus, only a portion develops scar tissue. This distinguishes FSGS from other types of glomerular scarring.
Glomeruli filter blood, allowing waste and excess water into urine while retaining proteins and blood cells. In FSGS, scarring damages their filtration, causing proteins to leak into the urine, a condition known as proteinuria. Damage primarily affects podocytes, specialized cells that maintain the filtration barrier. When podocytes are injured or lost, this barrier is compromised, leading to protein leakage into the urinary space.
Causes and Risk Factors
FSGS can arise from various underlying factors: primary, secondary, and genetic forms. Primary FSGS, also known as idiopathic FSGS, occurs when there is no identifiable cause for the kidney damage. An unknown circulating factor in the blood may directly injure podocytes, leading to scarring. This form accounts for a significant portion of FSGS cases and is often linked to an abnormal immune system response.
Secondary FSGS develops from other medical conditions, certain medications, or external factors. Examples include viral infections like HIV or Parvovirus B19, and drug use, such as anabolic steroids or heroin. Obesity is another risk factor, leading to increased blood flow and pressure within glomeruli, causing damage. Other conditions like sickle cell disease, lupus, or kidney anomalies present from birth can also contribute to secondary FSGS.
Genetic FSGS, also called familial FSGS, results from inherited genetic mutations that affect podocyte structure or function. Several genes involved in the glomerular filtration barrier have been identified. Genetic testing can help identify this type, particularly in individuals with a family history of kidney disease or those who do not respond to typical treatments.
Symptoms and Diagnosis
Symptoms of FSGS often develop gradually and may be subtle early on. A common symptom is swelling (edema), appearing in the legs, ankles, and around the eyes. Patients might also notice foamy or bubbly urine from excess protein (proteinuria). Other signs include sudden weight gain from fluid buildup, fatigue, and a poor appetite. High blood pressure and elevated cholesterol levels are often observed.
Diagnosis of FSGS involves a combination of tests. Urine tests detect protein levels; high protein levels are a hallmark. Blood tests also assess kidney function by measuring creatinine, albumin, and fats. While these tests can indicate kidney issues, a definitive diagnosis of FSGS requires a kidney biopsy. During a biopsy, a small kidney tissue sample is examined under a microscope, revealing characteristic focal and segmental scarring.
Management and Treatment Options
The primary goals of FSGS treatment are to reduce proteinuria, preserve kidney function, and manage associated symptoms. Treatment approaches vary depending on the type and severity of FSGS. For primary FSGS, medications that suppress the immune system often reduce inflammation and protect the glomeruli.
Corticosteroids, such as prednisone, are frequently the initial treatment choice for primary FSGS to calm the immune system. If corticosteroids are not effective or cause severe side effects, calcineurin inhibitors like cyclosporine or tacrolimus may be used. These medications also suppress immune responses and affect podocyte function. Other immunosuppressants, such as cyclophosphamide or mycophenolate mofetil, may be considered for resistant cases.
Supportive care measures are also important for managing FSGS. Medications like ACE inhibitors or angiotensin receptor blockers (ARBs) lower blood pressure and reduce protein leakage into the urine. Diuretics, often called “water pills,” eliminate excess fluid and reduce swelling. Dietary modifications, such as limiting sodium and controlling protein, also ease the burden on kidneys and manage symptoms.
Prognosis and Potential Complications
The long-term outlook for individuals with FSGS can vary significantly, influenced by cause, damage, and treatment response. While treatment can slow disease progression, glomerular scarring cannot be reversed. Some patients may achieve remission of proteinuria, which is associated with better long-term kidney survival.
Despite treatment, FSGS can lead to serious complications, including chronic kidney disease (CKD) and, in some cases, end-stage renal disease (ESRD). If ESRD develops, kidneys can no longer adequately filter waste, requiring dialysis or a kidney transplant. Many patients with FSGS may progress to kidney failure. Recurrence after a kidney transplant is also a possibility, negatively impacting transplant survival. Regular monitoring and adherence to treatment plans are important for managing the condition and identifying progression or complications.