CASE 195 (May 2022)

Clinical information

A 49-year-old man is evaluated due to edema of the lower limbs, headache, general malaise, and a purulent lesion on the first right toe. This lesion began a month earlier after a trauma caused by being pricked with a hobnail at work. History: arterial hypertension and non-insulin-requiring diabetes mellitus diagnosed more than 5 years ago. The patient has been receiving ampicillin-sulbactam for a week and NSAIDs for 2 weeks. He has also received captopril and metformin for years, which he takes irregularly.

On physical examination, blood pressure 160/100 mmHg, edema of the lower limbs, periungual purulent lesion in the first right toe, with cellulitis. There are no other skin lesions or other relevant findings.

Paraclinical: Hb: 12 mg/dL, Hct: 37%, leukocytes: 16,000/mm2, platelets 320,000/mm2; creatinine: 2.2 mg/dL, BUN: 38 mg/dL. ANAs negative, C3: 52 mg/dL, C4: 14 mg/dL. Studies for hepatotropic viruses and HIV were negative. Lipid profile: slightly increased triglycerides and total cholesterol; albumin: 3.4 g/dL. Normal protein electrophoresis. Anti-streptolysin O titer: <200 IU/mL. Blood cultures: negative. In urinalysis: protein 300 mg/dL, erythrocytes: 20-30/hpf, leukocytes: 8-10/hpf.

A renal biopsy was done, look at the images:

Figure 1. H&E, X400.

Figure 2. H&E, X400. All glomeruli have this appearance.

Figure 3. Masson´s trichrome stain, X400.

Figure 4. Masson´s trichrome stain, X400.

Figure 5. Masson´s trichrome stain, X1,000. Note the red (fuschinophilic) dot indicated by the arrow and its relationship to the basement membrane: subendothelial or subepithelial?.

Figure 6. Masson´s trichrome stain, X1,000. Here a larger fuschinophilic deposit (although it could also be part of an erythrocyte, sometimes it is not easy to know for sure)..

Figure 7. Methenamine-silver stain, X400. Multiple capillaries with obstruction of their lumen. There are no double contours.

Figure 8. Methenamine-silver stain, X400.

Figure 9. Direct immunofluorescence for IgA, X400.

Figure 10. Direct immunofluorescence for C3, X400.

Figure 11. Electron microscopy: segmental podocyte damage, basement membrane in general normal, although somewhat undulating towards the endothelial side; endothelium with loss of fenestrations. There is round electron-dense subepithelial material, not very well defined, in the upper-central part of the image. Original magnification, X2,100.

Figure 12. Electron microscopy: observe subepithelial electron-dense deposit in the upper left; endothelial edema with loss of fenestrations; an intracapillary leukocyte. Original magnification, X2,500.

Figure 13. Two very well defined subepithelial deposits; What name do we usually give them? Original magnification, X2,500.

Figure 14. Transmission electron microscopy, original magnification, X4,000.

Immunofluorescence for IgG: traces; IgM and C1q: negative.

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