Nephritic Syndrome Board Buzzwords: A Disease-by-Disease Guide

Every nephritic stem shares the same core: hematuria with RBC casts, hypertension, a rising creatinine, and protein under 3.5 g a day. The disease name comes from one extra clue. Hematuria 1 to 3 weeks after strep throat is poststreptococcal glomerulonephritis (PSGN), hematuria during a cold is IgA nephropathy, a malar rash is lupus nephritis, hemoptysis or a saddle nose is a rapidly progressive pattern, and hearing loss is Alport syndrome. Complement level and biopsy buzzwords confirm the call.

Once you've decided a stem is nephritic and not nephrotic, the work is picking the disease. If you still mix up the two syndromes, start with the nephritic vs nephrotic syndrome guide and come back. This article assumes you've made that split and goes disease by disease through the one or two clues each stem is built around.

What findings make a stem nephritic in the first place?

A nephritic stem shows glomerular inflammation. Look for cola-colored or tea-colored urine, RBC casts, dysmorphic red cells, hypertension, oliguria, and an elevated BUN and creatinine. Mild periorbital edema can appear, and protein usually sits below 3.5 g a day.

RBC casts are the single strongest finding. A red cell can only get molded into a tubular cast if it crossed the glomerulus, so casts localize the bleeding to the kidney's filter. Dysmorphic red cells (acanthocytes) point the same direction. Isolated hematuria with normal-shaped red cells and no casts should make you think about stones, bladder cancer, or a urinary tract source instead.

Hypertension and edema come from the same mechanism. Inflamed glomeruli filter less, GFR drops, and the kidney holds on to salt and water. That volume expansion raises blood pressure and puffs up the face. Contrast that with minimal change disease, where the leak is pure protein and the blood pressure is usually normal.

The buzzword cheat sheet

Read the table row by row and you'll notice that each disease leans on one extra-renal clue or one timeline. That clue is what the question writer plants, and it's usually in the first two lines of the stem.

Postinfectious glomerulonephritis: the timeline is the tell

PSGN is the classic nephritic syndrome of childhood. The patient is usually a child between about 5 and 12 years old who had a sore throat 1 to 3 weeks ago or impetigo 3 to 6 weeks ago. Now there's cola-colored urine, puffy eyes, and high blood pressure.

The buzzwords are "latent period," "low C3," and "positive ASO titer." After skin infection, anti-DNase B is the better marker, because ASO titers rise less after impetigo. On light microscopy the glomeruli are enlarged and hypercellular. Immunofluorescence is granular with IgG, IgM, and C3 (the "starry sky" or "lumpy-bumpy" pattern). Electron microscopy shows subepithelial immune complex humps.

PSGN is a type III hypersensitivity reaction. Treatment is supportive with salt restriction, diuretics, and blood pressure control. Most children recover fully. A board favorite is that treating strep pharyngitis with antibiotics prevents rheumatic fever but does not reliably prevent PSGN.

C3 should normalize within about 6 to 8 weeks. If it stays low past that window, the diagnosis is probably something else, usually MPGN or lupus, and biopsy becomes the next step.

Adults get a related picture called infection-related glomerulonephritis. Staph aureus is a common cause, and endocarditis-associated glomerulonephritis also runs with low complement. An older adult with a fever, a new murmur, and RBC casts should make you think about the heart before the throat.

IgA nephropathy and IgA vasculitis: hematuria that arrives with the cold

IgA nephropathy (Berger disease) is the most common primary glomerulonephritis worldwide. The classic patient is a young adult, often male, with episodes of gross hematuria that start during an upper respiratory or GI infection or within a day or two of it. The buzzword is "synpharyngitic." Between episodes the urine may show persistent microscopic hematuria.

Complement is normal, which is the fastest way to split it from PSGN. Serum IgA is elevated in some patients but is not diagnostic. Biopsy shows mesangial proliferation with mesangial IgA deposits on immunofluorescence. Disease course varies, and a subset of patients slowly progresses to chronic kidney disease over years.

IgA vasculitis (Henoch-Schönlein purpura) is the systemic version, and it's the most common childhood systemic vasculitis. The stem gives a child with palpable purpura on the buttocks and lower legs, joint pain, and abdominal pain, often after an upper respiratory infection. Platelets are normal, which separates it from ITP. Intussusception is the GI complication boards like to ask about. The kidney biopsy looks exactly like IgA nephropathy.

If a stem has purpura plus a kidney problem and you're not sure about the platelet count, the ITP vs TTP vs HUS vs DIC guide walks through the bleeding-disorder side of that differential.

Lupus nephritis: the systemic clues carry the stem

Lupus nephritis shows up in a young woman with a malar rash, photosensitivity, joint pain, serositis, or oral ulcers. Black and Hispanic women carry a higher risk. Anti-dsDNA is the antibody that tracks with kidney involvement, and both C3 and C4 run low because immune complexes activate the classical pathway.

Diffuse proliferative glomerulonephritis (class IV) is the most common and most severe form. Its buzzwords are "wire loop" capillary walls from subendothelial deposits and a "full house" immunofluorescence pattern (IgG, IgA, IgM, C3, and C1q). Membranous lupus nephritis (class V) presents as nephrotic syndrome instead, with subepithelial deposits.

Lupus is one of the diseases that can show nephritic and nephrotic features at the same time. A stem with RBC casts and more than 3.5 g of protein a day in a young woman is not a typo. It's pointing at lupus or MPGN. Treatment for class IV is immunosuppression, typically glucocorticoids plus mycophenolate or cyclophosphamide.

Rapidly progressive glomerulonephritis: sort it by immunofluorescence

Rapidly progressive glomerulonephritis (RPGN) is a pattern, not one disease. The kidney fails over days to weeks, and biopsy shows crescents in Bowman space. The crescents are made of fibrin, parietal epithelial cells, and macrophages. Board questions then ask you to sort RPGN into three immunofluorescence patterns.

Linear IgG (type I). This is anti-GBM disease. Antibodies target the alpha-3 chain of type IV collagen in glomerular and alveolar basement membranes. When the lungs are involved it's called Goodpasture syndrome, and the stem gives hematuria plus hemoptysis. It's a type II hypersensitivity reaction, complement is normal, and treatment is plasmapheresis plus glucocorticoids and cyclophosphamide.

Granular deposits (type II). This is immune complex disease that has progressed to crescents. PSGN, lupus nephritis, IgA nephropathy, and MPGN can all do this. The underlying disease still carries its own clue and complement pattern.

Pauci-immune, little or no staining (type III). This is ANCA-associated vasculitis. Granulomatosis with polyangiitis (GPA) gives chronic sinusitis, a saddle-nose deformity, otitis, hemoptysis, and cavitating lung nodules, with c-ANCA against proteinase 3. Microscopic polyangiitis gives lung and kidney disease without granulomas or upper airway disease, with p-ANCA against myeloperoxidase. Eosinophilic granulomatosis with polyangiitis (EGPA) adds adult-onset asthma, eosinophilia, and sometimes mononeuritis multiplex, also with p-ANCA.

The trap is that anti-GBM disease and GPA both put blood in the lungs and the urine. The tiebreakers are the upper airway findings for GPA, the ANCA type, and the linear versus pauci-immune immunofluorescence.

Membranoproliferative glomerulonephritis: the hepatitis and low C3 picture

MPGN often presents as a nephritic syndrome with protein that climbs into the nephrotic range. The biopsy buzzword is "tram-track," a double-contoured basement membrane created when mesangial cells grow into the capillary wall and lay down new membrane.

The immune complex form ties to hepatitis C and, less often, hepatitis B. Hepatitis C frequently brings mixed cryoglobulinemia along, and the stem may add palpable purpura, joint pain, and especially low C4. Deposits are subendothelial. The complement-mediated form, called dense deposit disease, links to C3 nephritic factor. That's an IgG autoantibody that stabilizes C3 convertase, so C3 stays persistently low.

Hereditary nephritis: Alport and thin basement membrane disease

Alport syndrome is the hereditary nephritis the boards test most. It's a defect in type IV collagen, most often X-linked (COL4A5), so the classic patient is a boy or young man. The stem pairs hematuria with sensorineural hearing loss and eye findings such as anterior lenticonus. A family history of kidney failure, often in male relatives, rounds it out.

Complement is normal. Electron microscopy shows a thinned, split, and laminated glomerular basement membrane, described as "basket-weave." Patients progress to kidney failure over time. The classic memory line is "can't see, can't pee, can't hear high C."

Thin basement membrane disease is the benign cousin. It causes persistent microscopic hematuria, often in several family members, with normal kidney function and no hearing or eye findings. EM shows a uniformly thin basement membrane without splitting. Boards use it as the reassuring answer when a stem gives familial hematuria and nothing else.

How do I pick the right disease when the buzzwords overlap?

Run the stem through the same clues I use for every question: age, acuity, unusual findings, matching timelines, laterality, labs and imaging, and the question part. Here is how they apply to nephritic syndrome.

1. Age. A school-age child points to PSGN or IgA vasculitis. A young adult points to IgA nephropathy, lupus, anti-GBM, or Alport. An older adult raises ANCA vasculitis and endocarditis-related disease.
2. Acuity. Kidney function falling over days to weeks means RPGN, and the next question is which immunofluorescence pattern.
3. Unusual findings. Extra-renal clues name the disease. Hemoptysis, saddle nose, purpura, malar rash, asthma, and hearing loss each map to one row of the cheat sheet.
4. Matching timelines. A 1 to 3 week gap after a sore throat is PSGN. Hematuria during the sore throat is IgA nephropathy.
5. Laterality. Glomerular disease hits both kidneys. A one-sided finding suggests a second problem, such as a stone or a mass.
6. Labs and imaging. Complement splits the list in half. ASO, anti-dsDNA, ANCA, anti-GBM antibodies, and hepatitis serologies each confirm one disease.
7. The question part. "Most likely immunofluorescence finding," "most likely EM finding," and "most appropriate treatment" are three different questions about the same patient, so read the last line first.

The complement split is worth memorizing as two short lists. Low complement fits PSGN, lupus nephritis, MPGN, cryoglobulinemia, and endocarditis-associated disease. Normal complement fits IgA nephropathy, IgA vasculitis, anti-GBM disease, ANCA vasculitis, and Alport syndrome.

These distinctions stick faster when you review your misses by pattern instead of one question at a time. The guide on how to review practice questions efficiently covers that habit. If you want renal review scheduled into the weeks you actually have left, the free Premeducated Study Plan Builder builds a day-by-day plan around your exam date.

Common traps on nephritic syndrome questions

Trap 1: Calling every post-infection hematuria PSGN. Check the gap. A latent period of weeks with low C3 is PSGN, while hematuria during the infection with normal complement is IgA nephropathy.

Trap 2: Missing the purpura. A child with abdominal pain and a rash on the backs of the legs is IgA vasculitis, and the kidney finding is the same as IgA nephropathy. Normal platelets keep you away from ITP.

Trap 3: Treating anti-GBM and GPA as the same disease. Both cause lung hemorrhage with nephritis. Sinus and nasal disease plus c-ANCA means GPA, and linear IgG means anti-GBM.

Trap 4: Forgetting C3 should recover. Low C3 lasting beyond about 8 weeks after a presumed PSGN points to MPGN or lupus. Biopsy is the next step.

Trap 5: Mixing up deposit locations. Subepithelial humps belong to PSGN. Subendothelial deposits belong to lupus class IV and immune complex MPGN. Mesangial deposits belong to IgA disease. Match the location to the clinical picture, not just the word.

Frequently asked questions about nephritic syndrome buzzwords

Which nephritic diseases have low complement?

PSGN, lupus nephritis, MPGN, cryoglobulinemic glomerulonephritis from hepatitis C, and endocarditis-associated glomerulonephritis all run with low complement. PSGN lowers C3 with a normal C4, while lupus lowers both C3 and C4. Cryoglobulinemia classically drops C4. IgA nephropathy, IgA vasculitis, anti-GBM disease, ANCA vasculitis, and Alport syndrome keep complement normal. Memorize the two lists, because complement is often the one lab that splits two look-alike stems.

What is the most common cause of glomerulonephritis worldwide?

IgA nephropathy is the most common primary glomerulonephritis worldwide. It classically causes episodes of gross hematuria during or within a day or two of an upper respiratory or GI infection, with normal complement. Biopsy shows mesangial IgA deposits. Many patients have a benign course, but a subset slowly progresses to chronic kidney disease, which is why persistent proteinuria and rising creatinine matter in follow-up.

How do I tell Goodpasture syndrome from granulomatosis with polyangiitis?

Both cause hemoptysis and nephritis, so look for the upper airway. GPA adds chronic sinusitis, a saddle-nose deformity, otitis, and cavitating lung nodules, with c-ANCA against PR3 and pauci-immune crescents on biopsy. Goodpasture syndrome has no upper airway disease, carries anti-GBM antibodies against type IV collagen, and shows linear IgG along the basement membrane. Anti-GBM disease is treated with plasmapheresis plus immunosuppression.

What does a "tram-track" appearance mean on a kidney biopsy?

Tram-track is the buzzword for membranoproliferative glomerulonephritis. Mesangial cells grow into the capillary wall and lay down new basement membrane, so the wall looks split into two parallel lines on silver stain. Boards tie the immune complex form to hepatitis C and hepatitis B, and the complement-mediated form (dense deposit disease) to C3 nephritic factor. Complement, especially C3, is low.

Why does Alport syndrome cause hearing loss?

The same type IV collagen network that builds the glomerular basement membrane is also found in the cochlea and the eye. The most common form is X-linked (COL4A5), so males are affected more severely. That's why the stem pairs hematuria with sensorineural hearing loss and eye findings such as anterior lenticonus. Electron microscopy shows a split, laminated "basket-weave" basement membrane, and complement is normal.

Is nephritic syndrome tested differently on COMLEX vs USMLE?

Both exams test the same diseases and the same buzzwords. Questions come in a few repeating types: name the disease from the stem, pick the immunofluorescence or electron microscopy finding, interpret the complement level, or choose the treatment. The cheat sheet and the stem-clue list in this guide cover all of those question types on either exam.

Related guides

• Nephritic vs nephrotic syndrome on COMLEX: how to tell them apart
• ITP vs TTP vs HUS vs DIC: how to differentiate them on board exams
• Acid-base disorder approach for boards
• How to review practice questions efficiently
• Doctor Lucas DO on YouTube: renal question breakdowns and high-yield clinical comparison videos