A patient has absent knee caps and nail abnormalities as shown. Which kidney lesion is common with these patients?
First, I remember that absent kneecaps, or patellar aplasia, and nail abnormalities are signs of a genetic disorder. The most common one that comes to mind is Ellis-van Creveld syndrome. That's a skeletal dysplasia. But wait, another possibility is another condition like Nail-patella syndrome. Let me think. Nail-patella syndrome is also known as hereditary onychoosteodysplasia. It's characterized by patellar hypoplasia or absence, nail dystrophy, and sometimes elbow abnormalities. And I think that this condition is associated with a specific kidney lesion.
Wait, the kidney lesion in Nail-patella syndrome is focal segmental glomerulosclerosis (FSGS). Because the gene involved in Nail-patella is LMX1B, which is a transcription factor. Mutations in LMX1B lead to defects in the development of the limbs and kidneys. The glomerular podocytes are affected, leading to FSGS. So if the patient has Nail-patella syndrome, they are at risk for FSGS.
Now, checking the options. The correct answer should be FSGS. The other options might be other kidney lesions like membranous nephropathy, IgA nephropathy, or minimal change disease. But the key here is the association with the specific syndrome. So the answer is FSGS.
Let me verify. Nail-patella syndrome is indeed linked with FSGS. The LMX1B gene is crucial for both limb and kidney development. So the correct answer is FSGS. The other options don't fit with the clinical presentation given.
**Core Concept**
This question tests the association between **Nail-patella syndrome** (hereditary onychoosteodysplasia) and its characteristic **focal segmental glomerulosclerosis (FSGS)**. The syndrome is caused by **LMX1B gene mutations**, which disrupt limb and renal development, leading to podocyte dysfunction in the kidneys.
**Why the Correct Answer is Right**
**Focal segmental glomerulosclerosis (FSGS)** is the hallmark renal lesion in Nail-patella syndrome. The **LMX1B transcription factor** regulates podocyte differentiation and glomerular basement membrane integrity. Mutations cause podocyte injury, resulting in proteinuria and FSGS. This condition is autosomal dominant and presents with **patellar aplasia/hypoplasia**, **nail dystrophy**, and **elbow abnormalities**.
**Why Each Wrong Option is Incorrect**
**Option A:** Membranous nephropathy is associated with autoimmune conditions (e.g., lupus) or secondary causes (e.g., malignancy), not Nail-patella syndrome.
**Option B:** IgA nephropathy is linked to recurrent hematuria and IgA deposition, unrelated to skeletal/nail abnormalities.
**Option C:** Minimal change disease occurs in children with nephrotic syndrome but lacks skeletal or nail pathology.
**Clinical Pearl / High-Yield Fact**
Never forget: **Nail-patella syndrome = FSGS** on renal biopsy. Remember the **"