The most common form of primary glomerular scaring is focal segmental glomerular sclerosis (FSGS). Segments of the glomeruli scattered throughout the kidney are typically affected and this is caused by either a systemic condition or an idiopathic or unknown factor.
Nephrotic syndrome or proteinuria without any other symptoms are the clinical features of FSGS, which is a progressive disease. It accounts for up to 2.3% of all end-stage renal disease (ESRD) cases.
Many patients with FSGS may not have any symptoms, but swelling of the ankle and leg (i.e., edema) is a common complaint in addition to hypertension, which proves difficult to manage. There is a high prevalence among those of African American descent, who are 2 to 3 times more likely than Caucasians presenting with nephrotic syndrome to have FSGS. Moreover, there is a higher incidence between the ages of 18 to 45 years old and males in comparison to females tend to be affected more.
Medical history and clinical examinations are the first steps taken in patients suspected of having FSGS. In order to distinguish between primary and secondary FSGS, disease presentation and associated medical conditions are very helpful. Suggestive of secondary FSGS are conditions, such as infections, hypertension and obesity, as well as proteinuria that is within nephrotic range, but not accompanied by full blown nephrotic syndrome.
Moreover, patients with secondary FSGS will tend to have gradually increasing amounts of protein in the urine. Hence, it is important to find out if the onset of the disease was sudden or subtle with gradual changes.
Drugs and medications that a patient is taking are important to identify, as several agents such as lithium and anabolic steroids may cause drug-induced FSGS. Laboratory tests for FSGS include biochemical panels in addition to serology and kidney function tests. A biopsy is definitive in order to establish the diagnosis as well as to identify the histological variant of FSGS.
Genetic testing for gene mutations associated with FSGS, especially those encoding proteins that maintain the viability of podocytes, although expensive, may also be done. Likewise, biomarkers like suPAR may also be employed to diagnose FSGS and predict its recurrence in those patients with primary FSGS who received kidney transplants.
Therapy for FSGS is aimed towards inducing total remission of urinary excretion of proteins, which leads to greater chances of preserving the long-term function of the kidney. It is crucial to make a distinction between primary and secondary FSGS, because different therapeutic approaches appear to be more effective in one as opposed to the other and vice versa.
Primary FSGS is presumed to be due to dysregulation of an autoimmune response and as such, immunosuppressive agents are advocated for treating this group of patients. These agents include calcineurin inhibitors, rituximab, and high-dose prednisone.
Attempts are made to eliminate the causative factor in secondary FSGS. In addition to treating the underlying condition, intraglomerular and systemic pressures are closely managed with agents, such as inhibitors of the renin-angiotensin system.
However, regardless of the etiology involved, all patients with nephrotic syndrome signs and symptoms and FSGS should be managed with diuretics, low-salt diets, and inhibitors of the renin-angiotensin system. These assist in reducing the risk of cardiovascular disease and long-term damage to the kidney.
Reviewed by Susha Cheriyedath, MSc