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Renal involvement in primary Sjögren’s syndrome (pSS) was first described in the 1960s, with reports of acquired defects in tubular function, in the setting of lymphocytic tubulointerstitial inflammation. Renal involvement in pSS is common, but is frequently undiagnosed due to its covert nature. It may manifest either as epithelial disease causing tubulointerstitial nephritis, or as an immune-complex glomerulopathy. Tubulointerstitial inflammation leads to acquired defects in tubular function, which may occur at multiple nephron segments. Treatment protocols lack evidence from randomized trials, and involve immunosuppression targeting B- and T-cells, which mediate both interstitial and glomerular disease to varying extents. In this chapter, we review the prevalence of renal involvement in pSS and its clinical manifestations, likely pathogenesis, and treatment.

The renal tubular acidoses are a collection of syndromes characterized by defective urinary acidification. These syndromes have classically caused some confusion, and many opine that the widely used numerical system (type 1, 2) should be abandoned. We consider distal renal tubular acidosis and proximal renal tubular acidosis separately, and briefly cover hypoaldosteronism. Distal (Type 1) renal tubular acidosis is a syndrome of hypokalaemia, metabolic acidosis, kidney stones, nephrocalcinosis, and osteomalacia or rickets. It is caused by failure of the acid secreting α‎‎‎-intercalated cells in the distal nephron. Proximal (Type 2) renal tubular acidosis is a syndrome of metabolic acidosis that is almost always accompanied by the Fanconi syndrome of glycosuria, phosphaturia, uricosuria, aminoaciduria, and low-molecular-weight proteinuria. It is caused by a failure of bicarbonate reabsorption by the proximal tubular cells. Type 3 or mixed renal tubular acidosis, as originally described, has vanished (or was originally incompletely described). It is sometimes used to describe a mutation of carbonic anhydrase II, which causes both proximal and distal renal tubular acidosis, as well as cerebral calcification and osteopetrosis. Type 4 or hypoaldosteronism is a syndrome of hyperkalaemia and mild metabolic acidosis. It is due to a lack of aldosterone or resistance to its action.

We present a case of post-transplantation Kaposi's sarcoma (KS) successfully treated by conversion to rapamycin. Clinical and histological resolution was observed within 6 months of commencing rapamycin. Also, vascular endothelial growth factor (VEGF) staining in the biopsy samples resolved following rapamycin therapy. Interestingly there was no expansion in cytotoxic T-lymphocyte (CTL) subsets observed during this period, as might be expected if this remission was due to immune reconstitution following reduction in immunosuppression. These data suggest that the resolution of tumour with rapamycin could be the result of the antiangiogenic, antiproliferative effects of rapamycin.