Focal segmental glomerulosclerosis overview

# Overview
Focal segmental glomerulosclerosis (FSGS) is a cause of nephrotic syndrome in children and adolescents, as well as an important cause of kidney failure in adults. Focal Segmental Glomerulosclerosis (FSGS) is a distinct finding and a descriptive report on the glomerular morphology seen in certain glomerular disease conditions. It is considered to be a glomerular podocytopathy .  Minimal change disease (MCD) is by far the most common cause of nephrotic syndrome in children:  MCD and primary FSGS may have a similar cause. Focal Segmental Glomerulosclerosis (FSGS) is very similar in presentation to Minimal Change Kidney Disease (MCD), in-fact both are podocytopathies but they are histological different with varying disease signs and symptoms.
The individual components of the name refer to the appearance of the kidney tissue on biopsy: focal - only some of the glomeruli are involved (as opposed to diffuse), segmental - only part of an entire glomerulus is involved (as opposed to global), glomerulosclerosis - refers to scarring of the glomerulus (a part of the nephron (the functional unit of the kidney)).
FSGS is a progressive form of renal disease, it has become the most common cause of GN-related ESRD in patients with End Stage Renal Disease (ESRD) in the United States.  It accounts for about 40% of adults and about 20% of pediatric cases of Nephrotic Syndrome in the United States. 
FSGS can be a primary or secondary cause of Nephrotic Syndrome. Primary FSGS can occur as an epithelial cell disorder characterized by podocytopathy of the glomeruli that may be related etiologically to minimal change disease. Secondary FSGS occurs due to previous glomerular injury or as a response to previous nephron loss from toxic effects of drugs, viral infections and chronic systemic diseases like diabetes mellitus, SLE, and other renal affecting autoimmune diseases.
Definitive diagnosis of FSGS is by kidney biopsy. High clinical suspicion is also very important in the diagnosis and differentiation of FSGS from MCD. MCD often presents with features of Nephrotic Syndrome like proteinuria, edema and hyperlipidemia while FSGS may present with hematuria, hypertension and decreased renal function which are common presentations of nephritic syndrome.

# Historical Perspective
Focal segmental glomerulosclerosis (FSGS) was first discovered by a Theodor Fahr, a German pathologist, in 1925, and he referred to it as "lipoid nephrosis with degeneration", showing a clear association to minimal change disease. In 1957, FSGS was then described by Dr. Arnold Rich, a pathologist at Johns Hopkins University.

# Classification
FSGS can be classified as primary and secondary disease depending on etiology, the course of the disease and histologic pattern.

# Pathophysiology
The pathophysiology of focal segmental glomerulosclerosis (FSGS) is based on two types of FSGS. Primary FSGS is also known as idiopathic FSGS, there is a hypothesis that suggests it occurs as a result of circulating immune activating factors interacting with the glomerular epithelium. The underlying pathogenesis of FSGS is fusion or effacement of the foot processes (podocytes) of the glomeruli and sclerosing of some parts of the glomeruli. These changes result in apoptosis and detachment of the glomerular basement membrane (GBM) resulting in subsequent loss of negative charge on podocytes and podocytopenia. Secondary FSGS is based on glomerular hypertrophy and hyperfiltration and over expression of inflammatory mediators such as, TGF-beta, PDGF and VEGF. The underlying pathogenesis can be based on multiple genetic mutations in NPHS1, NEPH1, NPHS2, WT1 and INF2 genes. Conditions associated with FSGS include, diabetes, HIV, sickle cell disease, nephrotic syndrome and minimal change disease. On microscopic histopathological analysis progressive changes seen are, foot process effacement, podocyte apoptosis, exposed GBM, capillary expansion and mesangial matrix proliferation.

# Causes

# Differentials

# Risk Factors

# Screening

# Epidemiology and Demographics

# Natural History, Complications, and Prognosis

# Diagnosis

## History and Symptoms

## Physical Examination

## Laboratory findings

## Imaging Findings

## Other Diagnostic Studies

# Treatment

## Medical Therapy

## Surgery

## Prevention