CRP-44

CRP-44

Clinical History

History of polymyositis, hypercalcemia and proteinuria. Negative serology.

Gross Description

Received in transport medium are two cores that measure 12 and 18 mm in length and 2 mm in diameter. A 5-mm fragment is taken for immunofluorescence, four 1-mm pieces are taken for EM, and the remaining tissue is submitted for light microscopy.

Pathology

Case CRP-044 PASH

Microscopic Description, Immunofluorescence, and Electron Microscopy

Microscopic Description

Light Microscopy

The specimen consists of two fragments of renal cortex that contain eight-six glomeruli in the three levels. Fourteen of these are obsolete, but the rest show minimal mesangial expansion and no proliferation. The capillary basement membranes are unremarkable with the silver stain. The PASH and trichrome stains show diffuse mild interstitial fibrosis and focal tubular atrophy. There are numerous lymphoid aggregates throughout the cortex, and there are also numerous noncaseating granulomata. Special stains for acid fast bacilli and fungi are negative with adequate controls. Occasional examples of mild tubulitis are identified. There is mild hyaline arteriosclerosis. The larger vessels are unremarkable.

Immunofluorescence

There are five glomeruli in the sections. There is 1+ segmental mesangial staining for IgM, IgA, C3 and lambda. There is no glomerular staining for IgG, Clq, albumin or kappa. There is no staining of the tubular basement membranes or vessels.

Electron Microscopy

Three thick sections are available, but there is only one glomerulus, which is unremarkable by light microscopy. Ultrastructural examination reveals no significant increase in mesangial matrix, and no mesangial deposits are identified. The glomerular basement membranes show focal mild thickening and wrinkling, and there is also focal fusion of the foot processes. No deposits are noted along the capillary loops.

Diagnosis and Comments

Kidney, needle biopsy - Granulomatous interstitial nephritis, consistent with sarcoidosis.

These features are most consistent with granulomatous interstitial nephritis. The differential diagnosis includes sarcoidosis and an allergic drug-induced reaction, but the clinical history is much more suggestive of sarcoidosis. There is only mild tubulointerstitial scarring, suggesting that significant recovery of renal function is possible with resolution of the acute interstitial inflammation.

Hypercalcemia is the state of having increased levels of calcium in the blood.

Protein in the urine is indicative of glomerular dysfunction.

Acid fast bacilli are not easily decolorized by acid during staining. This is characteristic of mycobacteria.