**Core Concept:** Finnish type of nephrotic syndrome is a rare form of nephrotic syndrome characterized by heavy proteinuria, hypoalbuminemia, hyperlipidemia, and edema. It is caused by mutations in genes associated with the nephrotic syndrome.

**Why the Correct Answer is Right:** The correct answer, D - mutations in the MECP2 gene, is related to a specific condition known as Nephrotic Syndrome with MECP2 mutations. MECP2 (Mechanistic Target of Rapamycin) is a protein that regulates cell growth, differentiation, and apoptosis. Mutations in the MECP2 gene lead to the production of an abnormal protein, causing a disruption in these processes resulting in the Finnish type of nephrotic syndrome.

**Why Each Wrong Option is Incorrect:**

A. Nephrotic syndrome associated with mutations in the NPHS1 gene (Nephrin) is not related to the Finnish type of nephrotic syndrome. Nephrin is a protein involved in the filtration barrier of podocytes in the glomerulus, while MECP2 mutations are associated with different clinical manifestations and renal pathology.

B. Mutations in the NPHS2 gene (Podocin) are associated with the Nephrotic Syndrome with NPHS2 mutations, not Finnish type nephrotic syndrome. Podocin is involved in the maintenance of the slit diaphragm between podocytes, while the Finnish type is linked to MECP2 mutations.

C. Mutations in the CD2AP gene (CD2-associated protein) are linked to Nephrotic Syndrome with CD2AP mutations, not Finnish type nephrotic syndrome. CD2AP is involved in the regulation of actin cytoskeleton rearrangement in podocytes, which is different from the pathophysiology of Finnish type nephrotic syndrome due to MECP2 mutations.

E. Nephrotic Syndrome associated with mutations in the INF2 gene (Infantile-onset autosomal recessive scleroderma) does not pertain to the Finnish type nephrotic syndrome. Inherited scleroderma is a different condition with distinct clinical features, while Finnish type nephrotic syndrome is caused by MECP2 mutations.

**Clinical Pearls:**

1. The Finnish type of nephrotic syndrome is a rare genetic disorder, while other types of nephrotic syndrome are caused by different genetic mutations and clinical presentations.
2. Understanding the genetic basis of nephrotic syndrome helps in distinguishing between various types and diagnosing the correct condition based on clinical and genetic factors.
3. Knowledge of these genetic mutations is important for differential diagnosis and appropriate management of patients with nephrotic syndrome and related clinical syndromes.