Nodular Cutaneous Amyloidosis at the Temple.

A 52-year-old woman presented with a large partially yellow and erythematous tumor on her right temple. She reported that it had grown over the last 4 years. Regional lymph nodes were impalpable. A punch biopsy showed eosinophilic material in the dermis and subcutis. Immunohistochemistry showed positive staining for kappa and lambda light chains. Electron microscopy showed the typical amyloid fibrils (7-10 nm in diameter). There was no evidence of systemic amyloidosis, paraproteinemia or underlying plasmacytoma. The tumor was completely removed via curettage. At follow-up, the patient presented in good health with no signs of relapse.

Deletion of von Hippel-Lindau protein converts renin-producing cells into erythropoietin-producing cells.

States of low perfusion pressure of the kidney associate with hyperplasia or expansion of renin-producing cells, but it is unknown whether hypoxia-triggered genes contribute to these changes. Here, we stabilized hypoxia-inducible transcription factors (HIFs) in mice by conditionally deleting their negative regulator, Vhl, using the Cre/loxP system with renin-1d promoter-driven Cre expression. Vhl (−/−(REN)) mice were viable and had normal BP. Deletion of Vhl resulted in constitutive accumulation of HIF-2α in afferent arterioles and glomerular cells and HIF-1α in collecting duct cells of the adult kidney. The preglomerular vascular tree developed normally, but far fewer renin-expressing cells were present, with more than 70% of glomeruli not containing renin cells at the typical juxtaglomerular position. Moreover, these mice had an attenuated expansion of renin-producing cells in response to a low-salt diet combined with an ACE inhibitor. However, renin-producing cells of Vhl (−/−(REN)) mice expressed the erythropoietin gene, and they were markedly polycythemic. Taken together, these results suggest that hypoxia-inducible genes, regulated by VHL, are essential for normal development and physiologic adaptation of renin-producing cells. In addition, deletion of Vhl shifts the phenotype of juxtaglomerular cells from a renin- to erythropoietin-secreting cell type, presumably in response to HIF-2 accumulation.