Neurofibromatose: estudo genético-clínico, avaliação quantitativa dos mastócitos e dos componentes da matriz extracelular em neurofibromas

Abstract

Neurofibromatosis (NF) is a neuroectodermal abnormality composed of a set of conditions having clinical manifestations which mainly affect the skin, eyes, bones, nervous system and eventually have repercussions on other internal organs. Its inheritance pattern is normally autosomally dominant and it has been considered one of the most frequent genetic diseases in the human race with a high penetration and variable expressiveness. This work studies the genetical-clinical aspects, makes a quantitative evaluation of the mastocytes and the extracellular matrix in neurofibromas in a group of thirty patients diagnosed with NF-1 and makes a comparison with a control group of ten normal individuals. The genetical-clinical evaluation confirmed the diagnosis of type 1 NF (NF-1) in all the patients. The main characteristics were neurofibromas, caféau-lait spots (CLS), Lisch nodules and axial or inguinal freckles. The multiple neurofibromas and Lisch nodules were considered to be exclusive to NF-1. Macrocephaly, in isolation, was not sufficient for the diagnosis of NF-1 and the other characteristics observed were considered complications. With the tissue from biopsies of both normal skin and neurofibromas of these patients, ten histologic sections were obtained. These were stained using hematoxylin-eosine, Gömöri trichrome, pricrosirius-hematoxylin, silver and iron-hematoxylin impregnation to evaluate the components of the extracellular matrix and staining using Toluidine blue to count the mastocytes. There was a significant increase in the number of mastocytes and the extracellular matrix was altered compared to the normal skin. This alteration was seen by the high cellularity associated with an increased density of fibrous components, specifically collagen type III, the scarcity or almost nonexistence of amorphous fundamental substance and the lack of elastic tissue. These findings seem to have an important role in the formation of neurofibromas and can help in the treatment of NF.