Kidney involvement in the Schnitzler syndrome, a rare disease

Abstract

The Schnitzler syndrome (SS) is a rare and underdiagnosed entity that associates a chronic urticarial rash, monoclonal IgM (or sometimes IgG) gammopathy and signs and symptoms of systemic inflammation. During the past 45 years, the SS has evolved from an elusive little-known disorder to the paradigm of a late-onset acquired auto-inflammatory syndrome. Though there is no definite proof of its precise pathogenesis, it should be considered as an acquired disease involving abnormal stimulation of the innate immune system, which can be reversed by the interleukin-1 receptor antagonist anakinra. It clearly expands our view of this group of rare genetic diseases and makes the concept of auto-inflammation relevant in polygenic acquired diseases as well. Increasing numbers of dermatologists, rheumatologists, allergologists, haematologists and, more recently, nephrologists, recognize the SS. The aim of this review is to focus on kidney involvement in the SS. Although the literature regarding kidney involvement in the SS is very poor it can be severe, as in our own case here reported, leading us to recommend the systematic search for nephropathy markers in the SS.

Keywords: Schnitzler syndrome; acute kidney injury; auto-inflammatory diseases; chronic urticarial rash; membranoproliferative glomerulonephritis; monoclonal IgM gammopathy.

Fig. 1.

The typical rash of the SS, which corresponds to a neutrophilic urticarial dermatosis: red eruptions consisting of flat macules are visible on the back and abdomen.

Fig. 2.

Kidney biopsy, light microscopy. Left and right upper panel: hypercellular glomeruli with endocapillary and mesangial proliferation (PAS staining). Left lower panel: double contour aspect with splitting and duplication of the glomerular basement membrane and expansion of the mesangial matrix (silver staining). Right lower panel: intimal thickening with lamellation of the elastic membrane of an artery (silver staining).

Fig. 3.

Kidney biopsy, immunofluorescence microscopy. Bright deposits scattered along the capillary walls and in the mesangium detected with an antibody to complement component C3.