True about fibronectin nephropathy are all except?
**Core Concept**
Fibronectin nephropathy is a rare cause of nephrotic syndrome characterized by the deposition of fibronectin in the glomerular basement membrane. This leads to a loss of the normal glomerular filtration barrier, resulting in massive proteinuria.
**Why the Correct Answer is Right**
Fibronectin nephropathy is a type of immune complex-mediated nephropathy, where fibronectin molecules are deposited in the glomeruli, causing damage. The exact mechanism is not well understood, but it is thought to involve the activation of the alternative complement pathway. The disease is often associated with the presence of anti-GBM antibodies, which can also be found in Goodpasture's syndrome.
**Why Each Wrong Option is Incorrect**
* **Option A:** Fibronectin nephropathy is indeed a rare cause of nephrotic syndrome, and the deposition of fibronectin in the glomerular basement membrane is a hallmark of the disease.
* **Option B:** The disease is not typically associated with the deposition of IgA, which is more commonly seen in IgA nephropathy.
* **Option C:** Fibronectin nephropathy is not a type of membranous nephropathy, which is characterized by the deposition of immune complexes on the subepithelial side of the glomerular basement membrane.
* **Option D:** The disease is not typically associated with the presence of C3 nephritic factor, which is often seen in dense deposit disease.
**Clinical Pearl / High-Yield Fact**
Fibronectin nephropathy is a rare cause of nephrotic syndrome, and its diagnosis often requires a combination of immunofluorescence, electron microscopy, and serological tests.
**Correct Answer: D. C3 nephritic factor is not typically associated with fibronectin nephropathy.**