**Question:** A linear pattern of immunoglobulin deposition along the glomerular basement membrane that can be demonstrated by immunofluorescence is typical of

A. IgA nephropathy
B. Membranous nephropathy
C. Membranoproliferative glomerulonephritis
D. Minimal change disease

**Core Concept:** Glomerular diseases are a group of disorders that affect the glomerulus, a filtration unit present in the kidneys. Immunofluorescence is a technique used to visualize the distribution of immune complexes in tissues, which can help in diagnosing various kidney diseases.

**Why the Correct Answer is Right:** A linear pattern of immunoglobulin deposition along the glomerular basement membrane is seen in Membranous Nephropathy (MBN), a renal disorder characterized by the accumulation of immune complexes (mainly IgG) on the glomerular basement membrane. This deposition causes a barrier to filtration, leading to proteinuria and hematuria. Membranous nephropathy is often associated with systemic diseases like systemic lupus erythematosus, antiphospholipid syndrome, or autoimmune diseases. Membranous nephropathy can also occur as a primary kidney disease.

**Why Each Wrong Option is Incorrect:**

A. IgA nephropathy (IgAN) primarily exhibits mesangial IgA deposition with or without immune complex deposition. The linear pattern is not a feature of IgAN.
B. Membranous nephropathy shares some clinical and laboratory features with Membranous Nephropathy (MBN); however, the deposition pattern is different. In Membranoproliferative glomerulonephritis (MPGN), immune complexes are found within the mesangium, not along the basement membrane.
C. Membranoproliferative glomerulonephritis (MPGN) is characterized by immune complex deposition in the mesangium, not the basement membrane. MPGN has a more diffuse pattern of immune complex deposition, distinct from the linear pattern seen in Membranous Nephropathy.
D. Minimal change disease (MCD) is characterized by a diffuse, non-specific glomerular lesion without immune complex deposition. The linear pattern seen in Membranous Nephropathy is distinct from the features of MCD.

**Clinical Pearl:** Membranous nephropathy is a clinical entity to consider in patients presenting with nephrotic syndrome, hypertension, and/or declining renal function. While its diagnosis depends on renal biopsy findings, the clinical context and response to treatment can guide the suspicion of Membranous Nephropathy.

**Correct Answer:** Membranous Nephropathy (MBN) is the correct answer because it exhibits a linear pattern of immunoglobulin and complement deposition along the glomerular basement membrane, as seen by immunofluorescence microscopy. This pattern is not present in the other options, making Membranous Nephropathy the correct answer.