Renal Pathology — MCQs
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Histologic sections of a kidney reveal patchy necrosis of epithelial cells of both the proximal and distal tubules with flattening of the epithelial cells, rupture of the basement membrane (tubulorrhexis), and marked interstitial edema. Acute inflammatory cells are not seen. What is the best diagnosis?
In which of the following conditions are bilateral contracted kidneys characteristically seen?
Which of the following drugs is a common cause of drug-induced interstitial nephritis?
Diffuse proliferative glomerulonephritis in lupus nephritis falls under which class?
What are the characteristic kidney changes seen in multiple myeloma?
A 36-year-old woman presents with increased malaise for 3 weeks and oliguria (<500 mL/day) for the past 4 days. On examination, her blood pressure is 170/112 mm Hg and she has peripheral edema. Urinalysis shows protein 1+ and hematuria (3+), with no glucose or ketones. Urine microscopy reveals RBCs and RBC casts. Her serum urea nitrogen is 39 mg/dL, and creatinine is 4.3 mg/dL. Serum complement levels (C1q, C3, and C4) are decreased. Renal biopsy with immunofluorescence microscopy shows a granular pattern of staining with antibody to C3. Which of the following types of hypersensitivity reactions is most likely causing her renal disease?
What is the cause of edema in glomerulonephritis?
In tubular necrosis, what is the typical ratio of urine to plasma creatinine?
Which of the following is FALSE about Alport syndrome?
A 29-year-old woman presents with a 3-day history of fever and sore throat. On examination, her temperature is 38°C. The pharynx is erythematous with yellowish tonsillar exudate. She is treated with ampicillin and recovers fully in 7 days. Two weeks later, she develops fever and a rash, with a slight decrease in urinary output. Her temperature is 37.7°C, and she has a diffuse erythematous rash on her trunk and extremities. Urinalysis shows pH 6, specific gravity 1.022, 1+ proteinuria, 1+ hematuria, and no glucose or ketones. Microscopic examination of the urine shows RBCs and WBCs, including eosinophils, but no casts or crystals. What is the most likely cause of her disease?
Renal Pathology Indian Medical PG Practice Questions and MCQs
Question 201: Histologic sections of a kidney reveal patchy necrosis of epithelial cells of both the proximal and distal tubules with flattening of the epithelial cells, rupture of the basement membrane (tubulorrhexis), and marked interstitial edema. Acute inflammatory cells are not seen. What is the best diagnosis?
- A. Acute pyelonephritis
- B. Acute tubular necrosis (Correct Answer)
- C. Chronic glomerulonephritis
- D. Chronic pyelonephritis
Explanation: ### Explanation **Correct Answer: B. Acute Tubular Necrosis (ATN)** **Why it is correct:** Acute Tubular Necrosis (ATN) is the most common cause of acute kidney injury (AKI) in hospitalized patients. The histological hallmark of ATN is the destruction of tubular epithelial cells [1]. This case describes **Ischemic ATN**, characterized by: 1. **Patchy involvement:** Unlike toxic ATN (which is continuous), ischemic ATN affects segments of both proximal and distal tubules [1]. 2. **Tubulorrhexis:** The rupture of the tubular basement membrane is a classic feature of ischemic injury [1]. 3. **Morphology:** Flattening of epithelial cells (regeneration) and interstitial edema are common [1]. The absence of acute inflammatory cells (neutrophils) helps distinguish this from an infectious process. **Why the other options are incorrect:** * **A & D. Pyelonephritis:** Acute pyelonephritis is characterized by **neutrophilic infiltration** (microabscesses) and white cell casts. Chronic pyelonephritis shows "thyroidization" of tubules and significant interstitial fibrosis. * **C. Chronic Glomerulonephritis:** This represents the end-stage of various glomerular diseases, characterized by hyalinized (sclerosed) glomeruli and global scarring, rather than acute tubular destruction. **NEET-PG High-Yield Pearls:** * **Ischemic ATN:** Patchy necrosis + Tubulorrhexis + Granular "Muddy Brown" casts in urine [1]. * **Toxic ATN:** Continuous necrosis (most prominent in the Proximal Convoluted Tubule) + Basement membrane usually remains intact. Common triggers: Gentamicin, Contrast dye, Myoglobin. * **Vulnerable Segments:** The Straight part of the Proximal Tubule (PST) and the Thick Ascending Limb (mTAL) are most susceptible to ischemia due to high metabolic activity [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 933-934.
Question 202: In which of the following conditions are bilateral contracted kidneys characteristically seen?
- A. Amyloidosis
- B. Diabetes mellitus
- C. Rapidly progressive glomerulonephritis
- D. Benign nephrosclerosis (Correct Answer)
Explanation: **Explanation:** The size of the kidneys is a critical diagnostic clue in renal pathology. **Benign Nephrosclerosis**, which occurs due to long-standing essential hypertension [1], characteristically presents with **bilateral, symmetrically contracted kidneys**. The underlying mechanism is hyaline arteriolosclerosis, leading to chronic ischemia, tubular atrophy, and interstitial fibrosis [2]. Grossly, the kidneys exhibit a "grain-leather" appearance due to fine surface scarring [2]. **Analysis of Options:** * **Amyloidosis (Option A):** Typically presents with **enlarged, pale, waxy kidneys** due to the massive deposition of amyloid protein in the glomeruli and interstitium. (Note: In very late stages, they may shrink, but "large" is the classic association). * **Diabetes Mellitus (Option B):** Early and mid-stage Diabetic Nephropathy is associated with **enlarged kidneys** (due to hyperfiltration and hypertrophy). Even in chronic renal failure due to diabetes, kidneys often maintain a relatively normal size compared to other end-stage renal diseases. * **Rapidly Progressive Glomerulonephritis (Option C):** This is an acute/subacute condition characterized by crescent formation. The kidneys are usually **enlarged and pale**, often with petechial hemorrhages (flea-bitten appearance), rather than contracted. **High-Yield Clinical Pearls for NEET-PG:** * **Small/Contracted Kidneys:** Chronic Glomerulonephritis (most common cause), Benign Nephrosclerosis, and Chronic Pyelonephritis (asymmetric contraction). * **Large Kidneys in Renal Failure:** Amyloidosis, Diabetes Mellitus, Polycystic Kidney Disease (PKD), Multiple Myeloma, and HIV-associated nephropathy. * **Flea-bitten Kidney:** Seen in Malignant Hypertension, PSGN, and Infective Endocarditis. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 541-542. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 943-945.
Question 203: Which of the following drugs is a common cause of drug-induced interstitial nephritis?
- A. Methicillin (Correct Answer)
- B. Cloxacillin
- C. Azlocillin
- D. Piperacillin
Explanation: **Explanation:** **Drug-Induced Interstitial Nephritis (DIIN)**, also known as Acute Tubulointerstitial Nephritis (ATIN), is a Type IV (delayed) hypersensitivity reaction occurring in the renal interstitium [1]. **Why Methicillin is the Correct Answer:** Among the penicillin group, **Methicillin** is the classic and most frequently cited prototype drug associated with DIIN in medical literature and pathology textbooks (e.g., Robbins). Although it is no longer used clinically due to its nephrotoxicity, it remains the "gold standard" answer for exams. The mechanism involves the drug acting as a hapten, binding to the tubular basement membrane and eliciting a T-cell mediated immune response [1]. **Analysis of Incorrect Options:** * **B, C, and D (Cloxacillin, Azlocillin, Piperacillin):** While almost any drug can theoretically cause ATIN, these specific penicillins are significantly less associated with this condition compared to Methicillin. In the context of NEET-PG, if multiple penicillins are listed, Methicillin is always the preferred historical and academic choice. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Fever, Rash, and Eosinophilia (present in only ~25-30% of cases) [2]. * **Urinary Findings:** Eosinophiluria (detected via Hansel stain) and sterile pyuria. * **Pathology:** The interstitium shows edema and infiltration by lymphocytes, macrophages, and characteristically, **eosinophils** [1]. * **Other Common Triggers:** NSAIDs (may cause minimal change disease simultaneously), Sulfonamides, Rifampin, and Proton Pump Inhibitors (PPIs) [2]. * **Key Distinction:** Unlike dose-dependent toxicity (e.g., Aminoglycosides), DIIN is **idiosyncratic** and not dose-related [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 940-941. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 538-539.
Question 204: Diffuse proliferative glomerulonephritis in lupus nephritis falls under which class?
- A. Class II
- B. Class III
- C. Class IV (Correct Answer)
- D. Class V
Explanation: **Explanation:** The International Society of Nephrology/Renal Pathology Society (ISN/RPS) classification of Lupus Nephritis (LN) is a high-yield topic for NEET-PG. **Correct Option (C): Class IV – Diffuse Proliferative Lupus Nephritis (DPGN)** Class IV is the most common and most severe form of lupus nephritis [1]. It is defined by involvement of **≥50% of glomeruli**. Pathologically, it presents with endocapillary proliferation, "wire-loop" lesions (subendothelial deposits), and hyaline thrombi [1]. It carries the worst prognosis if untreated and often presents with nephritic syndrome and declining renal function. **Incorrect Options:** * **Class II (Mesangial Proliferative LN):** Characterized by purely mesangial hypercellularity and matrix expansion with mesangial immune deposits. It has a good prognosis. * **Class III (Focal Proliferative LN):** Similar to Class IV but involves **<50% of glomeruli** [1]. It is essentially a less extensive version of DPGN. * **Class V (Membranous LN):** Characterized by diffuse thickening of the glomerular basement membrane due to subepithelial deposits. It typically presents with nephrotic-range proteinuria. **High-Yield Clinical Pearls for NEET-PG:** 1. **Most Common Class:** Class IV (Diffuse Proliferative) [1]. 2. **Most Common Cause of Death in SLE:** Renal failure (specifically Class IV). 3. **Wire-loop lesions:** Characteristic of Class IV (due to massive subendothelial deposits) [1]. 4. **Full House Pattern:** On Immunofluorescence (IF), there is positivity for IgG, IgA, IgM, C3, and C1q. 5. **Class VI:** Advanced Sclerotic LN (>90% globally sclerosed glomeruli; end-stage). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 230-232.
Question 205: What are the characteristic kidney changes seen in multiple myeloma?
- A. Hyaline casts (Correct Answer)
- B. Focal segmental glomerulosclerosis
- C. Membranoproliferative glomerulonephritis (MPGN)
- D. Fatty casts
Explanation: **Explanation:** In **Multiple Myeloma**, the most characteristic renal involvement is **Myeloma Nephrosis (Cast Nephropathy)** [1],[2]. This occurs because neoplastic plasma cells produce excessive amounts of monoclonal light chains (Bence-Jones proteins) [3]. These light chains are filtered by the glomerulus and reach the distal tubules, where they precipitate with **Tamm-Horsfall protein** to form obstructive, dense, and often "fractured" or "cracked" **Hyaline (waxy) casts** [2]. These casts are often surrounded by a multinucleated giant cell reaction, leading to tubular injury and renal failure [1],[2]. **Analysis of Options:** * **A. Hyaline casts (Correct):** These are the hallmark of myeloma kidney. While "hyaline" is a general term, in the context of myeloma, they appear as dense, eosinophilic, and laminated intratubular casts [1],[2]. * **B. Focal segmental glomerulonephritis (FSGS):** This is a pattern of glomerular scarring associated with conditions like HIV, obesity, or heroin use, but it is not a primary feature of Multiple Myeloma. * **C. Membranoproliferative glomerulonephritis (MPGN):** This is characterized by "tram-track" basement membrane splitting, usually seen in Hepatitis C or autoimmune diseases, not typically in myeloma. * **D. Fatty casts:** These contain lipid droplets and are characteristic of **Nephrotic Syndrome** (e.g., Minimal Change Disease), where there is significant lipiduria. **High-Yield Clinical Pearls for NEET-PG:** * **Bence-Jones Proteins:** These are light chains that precipitate at 40–60°C and redissolve on boiling. * **AL Amyloidosis:** Myeloma is the most common cause of systemic AL amyloidosis, which presents with Apple-green birefringence under polarized light [1],[2]. * **Diagnostic Clue:** If a patient has an unexplained high anion gap or renal failure with a "normal" dipstick (dipsticks detect albumin, not light chains), suspect Multiple Myeloma. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 618-619. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 942-943. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 616-617.
Question 206: A 36-year-old woman presents with increased malaise for 3 weeks and oliguria (<500 mL/day) for the past 4 days. On examination, her blood pressure is 170/112 mm Hg and she has peripheral edema. Urinalysis shows protein 1+ and hematuria (3+), with no glucose or ketones. Urine microscopy reveals RBCs and RBC casts. Her serum urea nitrogen is 39 mg/dL, and creatinine is 4.3 mg/dL. Serum complement levels (C1q, C3, and C4) are decreased. Renal biopsy with immunofluorescence microscopy shows a granular pattern of staining with antibody to C3. Which of the following types of hypersensitivity reactions is most likely causing her renal disease?
- A. Type I (IgE-mediated)
- B. Type II (Antibody-dependent cell-mediated cytotoxicity)
- C. Type III (Immune complex formation) (Correct Answer)
- D. Type IV (Delayed-type hypersensitivity)
Explanation: ### Explanation **Correct Answer: C. Type III (Immune Complex Formation)** The clinical presentation of **oliguria, hypertension, hematuria, and RBC casts** defines **Nephritic Syndrome**. In this patient, the rapid decline in renal function (rising creatinine) suggests **Rapidly Progressive Glomerulonephritis (RPGN)** [1]. The key diagnostic clues are: 1. **Low Serum Complement (C1q, C3, C4):** This indicates systemic activation and consumption of the complement cascade. 2. **Granular Immunofluorescence (IF):** A "lumpy-bumpy" granular pattern of C3 (and often IgG) signifies the deposition of pre-formed **antigen-antibody complexes** within the glomerulus [1], [2]. This mechanism is the hallmark of **Type III Hypersensitivity**. Common causes fitting this profile include Systemic Lupus Erythematosus (SLE) or Post-Streptococcal Glomerulonephritis (PSGN) [1], [3]. --- ### Why Other Options are Incorrect: * **Type I (IgE-mediated):** Involves mast cell degranulation and IgE. Clinically presents as anaphylaxis or asthma, not glomerulonephritis. * **Type II (Antibody-mediated):** Involves antibodies directed against fixed tissue antigens. In the kidney, this manifests as **Goodpasture Syndrome** (anti-GBM antibodies), which shows a **linear** (not granular) IF pattern and normal complement levels [1], [2]. * **Type IV (Cell-mediated):** Involves T-cells and macrophages. While T-cells play a role in chronic renal injury, the acute presentation with granular IF and low complement is classic for Type III. --- ### NEET-PG High-Yield Pearls: * **Granular IF:** Think Type III Hypersensitivity (e.g., PSGN, Lupus Nephritis, Membranous Nephropathy). * **Linear IF:** Think Type II Hypersensitivity (e.g., Goodpasture Syndrome). * **Pauci-immune (Negative IF):** Think ANCA-associated vasculitis (e.g., Wegener’s/GPA). * **Low Complement (Hypocomplementemia):** Common in PSGN, Lupus Nephritis, and MPGN. * **RBC Casts:** Pathognomonic for glomerular bleeding (Nephritic Syndrome). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, p. 915. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 526-527. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 536-537.
Question 207: What is the cause of edema in glomerulonephritis?
- A. Increased hydrostatic pressure.
- B. Sodium and water retention. (Correct Answer)
- C. Lymphatic obstruction.
- D. Reduced plasma oncotic pressure.
Explanation: In **Glomerulonephritis (Nephritic Syndrome)**, the primary mechanism of edema is **Sodium and Water Retention** [1]. ### Why Option B is Correct: The underlying pathology involves inflammatory damage to the glomerular capillaries, leading to a **decrease in the Glomerular Filtration Rate (GFR)**. This reduction in GFR triggers the kidneys to compensate by increasing the reabsorption of salt and water in the distal nephron. This results in primary fluid overload (hypervolemia), which increases hydrostatic pressure throughout the systemic circulation, causing fluid to leak into the interstitium [1]. This typically presents as **periorbital edema** or dependent edema. ### Why Other Options are Incorrect: * **Option A (Increased Hydrostatic Pressure):** While increased hydrostatic pressure is the *proximal* cause of fluid movement into tissues, it is a **consequence** of the primary sodium and water retention in glomerulonephritis. * **Option C (Lymphatic Obstruction):** This causes lymphedema (e.g., in Filariasis or post-mastectomy), which is usually non-pitting and unrelated to glomerular disease. * **Option D (Reduced Plasma Oncotic Pressure):** This is the hallmark of **Nephrotic Syndrome**, where massive proteinuria (>3.5g/day) leads to hypoalbuminemia [1]. In Nephritic Syndrome (Glomerulonephritis), proteinuria is usually sub-nephrotic and not severe enough to significantly drop oncotic pressure. ### NEET-PG High-Yield Pearls: * **Nephritic Syndrome Triad:** Hematuria (Cola-colored urine), Hypertension, and Oliguria/Edema. * **Edema Comparison:** In Nephritic syndrome, edema is due to **fluid overfill** (low GFR); in Nephrotic syndrome, it is due to **underfill** (low oncotic pressure) [1]. * **Most Common Cause:** Post-Streptococcal Glomerulonephritis (PSGN) is the classic example where this mechanism is tested. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 520-521.
Question 208: In tubular necrosis, what is the typical ratio of urine to plasma creatinine?
- A. Approximately 20 (Correct Answer)
- B. Approximately 40
- C. Between 20-30
- D. Between 30-40
Explanation: In renal pathology, distinguishing between **Prerenal Azotemia** and **Acute Tubular Necrosis (ATN)** is a high-yield topic for NEET-PG. The Urine/Plasma (U/P) Creatinine ratio is a vital marker of the kidney's concentrating ability and tubular integrity. ### **Explanation of the Correct Answer** **Option A (Approximately 20)** is correct because, in ATN, the tubular epithelial cells are damaged and lose their ability to reabsorb water and concentrate the glomerular filtrate. * Creatinine is filtered but not reabsorbed. In a healthy kidney, water is reabsorbed, concentrating the creatinine in the urine (U/P ratio >40). * In **ATN**, the "leaky" and dysfunctional tubules cannot concentrate the urine effectively. This results in a **U/P Creatinine ratio of <20**. [1] ### **Analysis of Incorrect Options** * **Option B (Approximately 40):** This value is characteristic of **Prerenal Azotemia**. In prerenal states, the tubules are structurally intact and respond to hypovolemia by reabsorbing maximum water, thereby concentrating the urine creatinine to high levels (>40). [1] * **Options C & D:** These represent intermediate ranges. While clinical cases can overlap, for examination purposes, a ratio **<20** strongly points toward intrinsic renal damage (ATN), while **>40** points toward prerenal causes. ### **Clinical Pearls for NEET-PG** To differentiate Prerenal Azotemia from ATN, remember this high-yield table: | Feature | Prerenal Azotemia | Acute Tubular Necrosis (ATN) | | :--- | :--- | :--- | | **U/P Creatinine Ratio** | **> 40** | **< 20** | | **Fractional Excretion of Na (FeNa)** | < 1% | > 2% | | **Urine Sodium (UNa)** | < 20 mEq/L | > 40 mEq/L | | **Urine Osmolality** | > 500 mOsm/kg | < 350 mOsm/kg | | **Microscopy** | Hyaline casts | **Muddy brown granular casts** | **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 933-934.
Question 209: Which of the following is FALSE about Alport syndrome?
- A. Sensory neural deafness
- B. Keratoconus
- C. Megalocornea
- D. Thrombocytosis (Correct Answer)
Explanation: **Explanation:** Alport Syndrome is a hereditary nephritis caused by mutations in the genes encoding the **α-chains of Type IV collagen** (most commonly *COL4A5*, X-linked) [1]. Type IV collagen is a crucial structural component of basement membranes in the glomerulus, cochlea, and eye. **Why Option D is Correct:** **Thrombocytosis** is not a feature of Alport syndrome. In fact, a specific variant of Alport syndrome (associated with *MYH9* gene mutations, such as **Fechtner syndrome**) is characterized by **thrombocytopenia** (low platelet count) and giant platelets, rather than thrombocytosis. **Why the other options are Incorrect:** * **A. Sensory neural deafness:** This is the most common extra-renal manifestation [1]. The defect in Type IV collagen affects the basement membrane of the Organ of Corti in the cochlea, leading to progressive high-frequency hearing loss. * **B. Keratoconus:** Ocular manifestations are common due to thinning of the corneal stroma and lens capsule. Keratoconus (conical protrusion of the cornea) and **anterior lenticonus** (pathognomonic) are classic findings. * **C. Megalocornea:** While less common than lenticonus, various corneal abnormalities, including megalocornea and posterior polymorphous corneal dystrophy, have been documented in Alport patients. **High-Yield Clinical Pearls for NEET-PG:** * **Inheritance:** 80% are **X-linked Dominant** (mutations in *COL4A5*). [1] * **Electron Microscopy (EM):** The gold standard for diagnosis. It shows a characteristic **"Basket-weave appearance"** due to irregular thickening, thinning, and splitting of the Glomerular Basement Membrane (GBM). * **Clinical Triad:** Hereditary nephritis (hematuria/ESRD), sensorineural deafness, and ocular defects (Anterior lenticonus). * **Immunofluorescence:** Shows absence of staining for α3, α4, and α5 chains of Type IV collagen [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 929-930.
Question 210: A 29-year-old woman presents with a 3-day history of fever and sore throat. On examination, her temperature is 38°C. The pharynx is erythematous with yellowish tonsillar exudate. She is treated with ampicillin and recovers fully in 7 days. Two weeks later, she develops fever and a rash, with a slight decrease in urinary output. Her temperature is 37.7°C, and she has a diffuse erythematous rash on her trunk and extremities. Urinalysis shows pH 6, specific gravity 1.022, 1+ proteinuria, 1+ hematuria, and no glucose or ketones. Microscopic examination of the urine shows RBCs and WBCs, including eosinophils, but no casts or crystals. What is the most likely cause of her disease?
- A. Deposition of immune complexes with streptococcal antigens
- B. Formation of antibodies against glomerular basement membrane
- C. Hematogenous dissemination of septic emboli
- D. Hypersensitivity reaction to ampicillin (Correct Answer)
Explanation: ### **Explanation** The clinical presentation is a classic case of **Acute Tubulointerstitial Nephritis (ATIN)**, specifically drug-induced hypersensitivity. **1. Why Option D is Correct:** The patient developed a triad of **fever, rash, and eosinophiluria** approximately two weeks after starting **ampicillin** [1], [2]. ATIN is a Type IV (delayed) hypersensitivity reaction [1]. It is not dose-dependent and typically occurs 2–15 days after drug exposure [2]. Common triggers include NSAIDs, Penicillins (like ampicillin), Sulfonamides, and Diuretics [2]. The presence of **eosinophils in the urine** (Hansel’s stain) is a highly specific diagnostic clue for drug-induced ATIN [1]. **2. Why Other Options are Incorrect:** * **Option A:** Refers to **Post-Streptococcal Glomerulonephritis (PSGN)**. While the timing (2 weeks post-pharyngitis) fits, PSGN typically presents with nephritic syndrome (hypertension, edema, and **RBC casts**) [3], [4]. It does not cause a rash or eosinophiluria. * **Option B:** Refers to **Goodpasture Syndrome**. This involves anti-GBM antibodies causing rapidly progressive glomerulonephritis and pulmonary hemorrhage [3], [5]. It is not associated with recent antibiotic use or eosinophiluria. * **Option C:** Septic emboli (e.g., from Infective Endocarditis) would cause localized infarcts or abscesses, usually presenting with more severe systemic illness, heart murmurs, and positive blood cultures, rather than a diffuse hypersensitivity rash. ### **NEET-PG High-Yield Pearls** * **Classic Triad of ATIN:** Fever, Rash, and Eosinophilia (seen in only ~30% of cases, but high-yield for exams) [2]. * **Urinalysis:** Look for **sterile pyuria** (WBCs without bacteria) and **eosinophiluria** [1]. * **Key Drugs:** Remember the "5 P's": **P**ee (Diuretics), **P**ainkillers (NSAIDs), **P**enicillins/Cephalosporins, **P**roton Pump Inhibitors, and Rifam**p**in [2]. * **Pathology:** Interstitial edema and infiltrate (lymphocytes, plasma cells, and eosinophils) with **sparing of the glomeruli** [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 940-941. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 538-539. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, p. 915. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 914-915. [5] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 537-538.
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Glomerular Diseases
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