L’amylose à lysozyme

Abstract

Lysozyme amyloidosis is a non-neuropathic hereditary amyloidosis identified in 1993. About fifty cases of this rare, probably under-diagnosed disease are reported. Lysozyme amyloidosis has a very broad spectrum of clinical manifestations. Sicca syndrome is often the first symptom, preceding the diagnosis by several years. Every part of the digestive tract can be involved with different grades of severity. The hallmark of this amyloidosis is the usually life-threatening spontaneous hepatic rupture. Renal involvement is frequent and progresses towards end-stage renal failure and dialysis. Skin, lymph nodes, and spleen can also be affected. More recently, cardiac and pulmonary involvement was reported. Phenotypic heterogeneity and incomplete penetrance make the clinical diagnosis difficult. Amyloid deposits are revealed by Congo red staining with birefringence under polarized light. They can be limited or diffuse and lead to the progressive destruction of the architecture of an organ and its failure. Immunohistochemistry reveals the nature of the amyloid variant by identifying antilysozyme antibodies in the deposit. Up to know, eight pathologic mutations and one polymorphism involving exons 2, 3, and 4 of the lysozyme gene have been identified. The transmission is autosomal dominant, without any genotype-phenotype correlation. The therapeutic options are limited and based on symptomatic or supportive treatment. Renal and hepatic transplant has proved its benefits with a prolonged graft survival. A long term regular and multidisciplinary follow-up is required.