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Tubulointerstitial Nephritis with Uveitis

Tubulointerstitial nephritis with uveitis (TINU) was first described as a distinct entity by Dobrin, et al. in 1975. TINU primarily affects young females (median age 15 years) who commonly have associated systemic signs and symptoms of the disease including weight loss, fever, fatigue, malaise, abdominal or flank pain, arthralgias or myalgias, and headache. The syndrome is likely underdiagnosed as a result of the asynchronous presentation of the renal and ocular symptoms. In fact, the ocular symptoms lag behind the interstitial nephritis diagnosis in two-thirds of cases by up to 14 months. TINU should be considered a diagnosis of exclusion only...

Trichrome Staining in Deposits

While the trichrome stain is best known for assessing the extent of interstitial fibrosis, it is a versatile stain with many applications. In this high-magnification image of a proliferative glomerulonephritis, the arrow points to red-pink (i.e. “fuchsinophilic”) subepithelial deposits along the blue-stained glomerular capillary wall. The corresponding immunofluorescence image from the same case shows extensive capillary wall IgG deposits (Fig. 2). If a particular biopsy lacks glomeruli or tissue for immunofluorescence studies, the trichrome stain can provide a useful clue that an immune complex-mediated disease process is present. In addition, the trichrome stain can be helpful in the identification of fibrin,...

Tenofovir

A wide variety of prescription and over the counter drugs may cause toxic injury to the renal tubular epithelium. Given the morphologic overlap of acute tubular injury secondary to different etiologic agents, determination of the offending drug is usually not possible by morphology alone and clinico-pathological correlation is often, if not always, needed. However, there are certain drugs that yield a quite characteristic pattern of injury which enables the pathologist to suggest a possible etiology. Such is the case of tenofovir, a nucleotide analog reverse-transcriptase inhibitor frequently used to treat and prevent HIV infection. Histologic findings in patients with tenofovir-associated...

IgAN and Acute Tubular Injury with Legionella

Acute kidney injury in the setting of Legionella pneumonia. This biopsy is a middle-aged person with Legionella pneumonia who developed acute kidney injury. Early in the hospitalization, the baseline creatinine was 1.0 mg/dl. However, the creatinine rose to 6.5 over 5 days and Nephrology was consulted. Urinalysis showed microscopic hematuria and 2+ proteinuria. The creatinine increased to 7.5 and a biopsy was done. Serologic studies were ordered and were pending at the time of biopsy. The images provided show a combination of acute tubular injury (Image 1), mild mesangial matrix expansion (Image 2) and mesangial IgA deposits (Image 3). While...

2,8-Dihydroxyadenuria

Adenine phosphoribosyltransferase (APRT) deficiency results from an autosomal recessive enzyme defect of purine metabolism and leads to 2,8-dihydroxyadenine (2,8-DHA) crystalline nephropathy. The clinical presentation of this often misdiagnosed disease is widely variable among patients homozygous for APRT mutations, ranging from asymptomatic in some to reddish-brown diaper stains in infants to recurrent nephrolithiasis, and even CKD in the absence of nephrolithiasis. 2,8-DHA nephropathy has also been reported to recur in the renal allograft resulting in rapid allograft failure. Prompt and accurate diagnosis of this disorder is important so that treatment through pharmacologic inhibition of xanthine dehydrogenase can be initiated. The morphologic findings...

Extramedullary Hematopoiesis

This renal biopsy shows extramedullary hematopoiesis (EMH), which is the presence of hematopoietic elements (erythroid, myeloid, and/or megakaryocytic) found outside of the bone marrow. The larger circle contains mostly erythroid precursors and the arrow identifies an immature megakaryocyte. Generally, the histologic differential diagnosis includes acute interstitial nephritis (erythroid precursors may be confused with mature inactive lymphocytes) and even some types of lymphoma (megakaryocytes may resemble atypical or malignant lymphoid cells). In difficult cases, lineage-specific immunohistochemical stains can be used to confirm the presence of hematopoietic cells. Recognizing EMH is important because it often signifies impaired bone marrow function due to...

Pushing Glass (July 25, 2017)

The patient is a 64-year-old female who presents with 4.5 grams of proteinuria, hematuria, and a creatinine of 1.5. She has a history of hypertension and coronary artery disease. What is the best diagnosis? A. Arterionephrosclerosis B. Focal Segmental Glomerulosclerosis C. Amyloidosis D. Fibrillary Glomerulonephritis The best answer is C: Amyloidosis. The biopsy, at first glance, looks like a subcapsular scar with diffuse global glomerulosclerosis. In this setting, arterionephrosclerosis would provide a good explanation for this distribution of fibrosis especially with the severe arteriosclerosis seen in the vessel. FSGS is also a consideration and can produce segmental scars with extensive...

Caseating Granuloma

Incidental findings on renal biopsies are not uncommon. The presented image shows a caseating granuloma within the renal medulla of a diabetic patient without known history of infection. The lesion shows central necrosis surrounded by palisading histiocytes and scattered lymphocytes. Caseating granulomata are highly suspicious for mycobacterial or fungal infections. While AFB, Auramine-Rhodamine and GMS stains are negative in this case, due to the relative insensitivity of these stains, ruling out an infection clinically is warranted. In those cases with non-caseating granulomata, the differential diagnosis would expand to include drug reactions, sarcoidosis and other autoimmune disorders. In such cases, performing...

Diagnose This! (July 24, 2017)

What is your diagnosis?       ​   ​ ​   ​   ​ ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​ ​   ​ ​   ​ ​   ​ ​     ​   ​  ...