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Persistent defective membrane trafficking in epithelial cells of patients with familial hemophagocytic lymphohistiocytosis type 5 due to STXBP2/MUNC18-2 mutations§

Authors


  • Conflict of interest: Nothing to declare.

  • Authorship: We thank Polina Stepensky and Carsten Posovszky for conception and drafting the article, collecting the case histories and material together with Jack Bartram, Ortraud Beringer, Manfred Hoenig, K. Amann and T. Barth for histopathological K. Amann, P. Walther, and C. Posovszky for electron microscopy and U. Zur Stadt for molecular genetic workup.

  • §

    We thank Kai Lehmberg, Alan D. Philips, Ansgar Schulz, Persis Amrolia, Michael Weintraub, and Klaus-Michael Debatin for revising the article critically for important intellectual content.

Abstract

Background

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare primary immune disorder defined by mutations in the syntaxin binding protein 2 (STXBP2) alias MUNC18-2. Despite defective immunity and a hyper-inflammatory state, clinical findings such as neurological, gastrointestinal, and bleeding disorders are present in a significant number of patients and suggest an impaired expression and function of STXBP2 in cells other than cytotoxic lymphocytes.

Procedure

We investigated four patients with FHL5 suffering from severe enteropathy and one of whom also had renal tubular dysfunction despite successful hematopoietic stem cell transplantation (HSCT). Gastrointestinal and renal biopsy specimens were analyzed by immunohistochemistry and electron microscopy.

Results

Histopathology revealed an intracytoplasmatic accumulation of PAS-positive granules and an enlarged intracytoplasmatic CD10-positive band along the apical pole of enterocytes. Electron microscopy revealed short microvilli and granules filled with electro lucent material. In addition, we described mildly dilated renal tubules and electron micrographs displayed a higher number of cytoplasmic inclusions, electrodense lysosomal and electrolucent endosomal vesicles.

Conclusion

Mutations in STXBP2 do not only affect cytotoxic T lymphocytes but also cause changes in the intestinal and renal epithelium resulting in severe, osmotic diarrhea and renal proximal tubular dysfunction. These defects persist after successful treatment of hemophagocytic lymphohistocytosis by HSCT. Clinical manifestations in FHL5 patients despite successful HSCT may therefore be related to defective membrane trafficking in the gut and kidney. Pediatr Blood Cancer 2013; 60: 1215–1222. © 2013 Wiley Periodicals, Inc.

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