Many entities affect specifically the tubulointerstitium, most often sparing the glomeruli and vessels, but exact subclassification is difficult because the histologic findings may have overlapping features. Frequently biopsies are performed shortly after symptoms manifest (in the acute phase). There is controversy in the terminology of chronic lesions; for example the term chronic pyelonephritis, particularly in the pediatric population, has fallen out of favor, replaced by other terms such as reflux nephropathy. However, careful examination and clinicopathologic correlation helps to pinpoint the cause and guide appropriate patient management. In this chapter, the focus is on the histopathology of acquired and hereditary tubulointerstitial diseases in native kidneys.

Sjögren’s syndrome is an autoimmune disease that predominantly affects women. Sjögren’s syndrome can present as Primary Sjögren Syndrome (PSS) if it is isolated syndrome, or as Secondary Sjögren Syndrome (SSS) if associated with other connective tissue diseas. Sjögren’s syndrome affects the nervous system in approximately 20% of cases and, of these, only 2-5% present central nervous system involvement. A few cases of ischemic and / or hemorrhagic stroke associated with Sjögren's syndrome as the first symptomatic manifestation of the disease, have been reported. We discuss a case of a 50-year-old woman with a history of transient ischemic attacks, admitted in emergency room because of acute onset of speaking difficulties and a loss of strength in the right arm, successfully treated with intravenous thrombolysis. Brain magnetic resonance imaging showed recent ischemic lesions in the left-brain hemisphere and MR angiography showed multiple arteries stenosis. Few weeks later, the neurological and MRI picture worsened. The laboratory screening tested the presence in the serum of Sjögren Syndrome specific antibodies. Immunosuppressive drugs (IV cyclophosphamide and oral prednisone) was started with transient clinical response. Following a clinical relapse, the patient was treated with rituximab, but the severe cardio-pulmonary and neurological complications led the patient to death. Cerebral arteries vasculitis of small and medium-size vessel is likely the pathogenetic mechanism of the ischemic damage in patients with PSS. Advances in knowledge of the molecular mechanisms involved in the etiopathogenesis of primary Sjögren syndrome may allow the development of highly selective and more effective therapies