CRP-10

CRP-10

Clinical History

The patient is a 28 year old female. 17 weeks pregnant. Urinary protein 2 g/day. Three consecutive serum creatines were 0.8, 3.8 and 0.7. Negative ANA; normal complements. No systemic complaints.

Gross Description

Received in transport media are two cores measuring 6 and 13 mm in length and 2 mm in diameter. Three 1-mm pieces are taken for EM, and the remainder is bisected and equally divided for immunofluorescence and light microscopy.

Pathology

Case CRP-010 Silver

Microscopic Description, Immunofluorescence, and Electron Microscopy.

Microscopic Description

Light Microscopy

The specimen consists of two fragments of renal cortex that contain eighty-eight glomeruli in the three levels. One of these is obsolete, and five show a distinctive lesion at the tip of the glomerular tuft that has been called "glomerular tip lesion." These lesions are all adjacent to the opening of the proximal tubule, and the involved segments consist of foam cells within dilated capillaries, sometimes accompanied by hyalinosis. Some of the lesions form small adhesions to the capsule, and others appear to be prolapsed into the tubule. Many of the glomeruli show mild mesangial expansion and mild hypercellularity, but there are no segmental proliferative lesions. No glomerular necrosis is identified. There are no cellular or fibrous crescents. Silver and PASH stains show no significant thickening of the capillary basement membranes, other than in the region of the glomerular tip lesions. The trichrome stains shows no significant interstitial fibrosis or tubular atrophy. There are no inflammatory infiltrates. The vessels are unremarkable.

Immunofluorescence

There are at least twenty-two glomeruli in the sections. None of these are obsolete, and no segmental lesions are identified. There is trace granular mesangial staining for IgM, IgA, and kappa light chain. The staining for IgM is definitely slightly stronger than the IgA. There is no glomerular staining for IgG, Clq, C3 or lambda light chain. The mesangial staining is focal rather than diffuse. Tubular epithelium contains numerous albumin droplets. There is no staining of the tubular basement membranes. Blood vessels show focal thickening for C3. The entire panel of stains was repeated, and the trace positivity was confirmed.

Electron Microscopy

Three thick sections containing a total of five glomeruli are available. These show mild mesangial expansion and hypercellularity, but no tip lesions are identified. Ultrastructural examination reveals no significant thickening of the glomerular basement membranes, although there is diffuse fusion of the epithelial foot processes. Rare, small, ill-defined electron dense deposits are identified in the mesangium, but none are noted in the capillary basement membranes.

Diagnosis and Comments

Kidney, needle biopsy - Focal segmental glomerulosclerosis, glomerular tip lesion variant

This case is difficult to interpret. In my opinion, these findings are most consistent with glomerular tip lesion, which is generally considered a morphologic variant of focal segmental glomerulosclerosis. However, some authors feel that the tip lesion simply represents a structural complication of proteinuria in patients with minimal change nephropathy. Furthermore, the prognostic significance of the tip lesion remains uncertain. Some nephrologists believe that this lesion is a potentially responsive form of the idiopathic nephrotic syndrome, and there are reports that patients respond better to steroid therapy than those with classic FSGS. However, the response is not as good as in patients with minimal change nephropathy. Two other possibilities that must be considered are lupus nephritis and IgA nephropathy. Although the immunofluorescence staining was very weak for both IgA and IgM, the IgA staining appears to be less than the IgM, and I think IgA nephropathy is very unlikely. I cannot completely rule out very early mesangial lupus nephritis, although I consider it unlikely. Close clinical follow-up and serologic monitoring is recommended. On the basis of the morphology in this biopsy, it seems very likely that the serum creatinine value of 3.8 was a lab error.

An infiltrate is an accumulation of cells in the lung parenchyma--this is a sign of pneumonia.

Protein in the urine is indicative of glomerular dysfunction.