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Abstract(s)
As ictioses são um grupo, clinica e etiologicamente heterogéneo, de dermatoses, classificado como desordens de queratinização ou cornificação. São consequência de defeitos metabólicos que resultam numa anormal diferenciação da epiderme, conferindo à superfície cutânea um aspeto descamativo peculiar, evocativo de escamas de peixe, de onde deriva a designação da doença (do grego ichthys i.e. peixe).
O objetivo desta dissertação é fazer um ponto da situação sobre os conhecimentos e avanços atuais associados às ictioses, incidindo numa perspetiva histórica até à atualidade e abordando, sucessivamente: Classificação, Etiopatogenia, Apresentação Clínica, Diagnóstico, Estratégias Terapêuticas e Perspetivas Futuras.
As ictioses têm vindo a ser classificadas de diferentes formas, ao longo do tempo, com base nos conhecimentos alcançados acerca da sua etiopatogenia, manifestações clínicas, dados genéticos e moleculares e novas caracterizações histopatológicas. Atualmente, um dos princípios utilizados para classificar as ictioses é baseado no facto da doença ser resultante de determinação genética, de caráter hereditário – Ictioses Hereditárias – ou ser consequência de patologias sistémicas, de índole adquirida – Ictioses Adquiridas.
Relativamente às ictioses hereditárias, estas subdividem-se em dois grandes grupos, as Ictioses Não Sindromáticas (a alteração genética evidencia-se em exclusivo na pele), e as Ictioses Sindromáticas, (a dermatose ocorre em associação com anomalias noutros sistemas orgânicos).
As ictioses não sindromáticas, por sua vez, dividem-se noutros três grandes grupos principais, as Ictioses Comuns, as Ictioses Congénitas Autossómicas Recessivas e as Ictioses Queratinopáticas.
No que diz respeito à etiopatogenia, durante as duas últimas décadas, têm vindo a ser descobertas as causas genéticas de grande parte dos 36 tipos de ictioses hereditárias. Quanto às respetivas bases moleculares, apenas algumas se encontram por identificar.
As alterações cutâneas associadas a este tipo de dermatoses caracterizam-se, clinicamente, por hiperqueratose, descamação cutânea difusa ou ambas. A apresentação clínica é variável, não só na gravidade (desde xerodermia até formas com elevado risco de morte neonatal), mas também na idade de manifestação e nos sintomas associados.
O estabelecimento de um diagnóstico específico pode afigurar-se difícil, dada a complexa heterogeneidade clinicopatológica das ictioses e a diversidade dos mecanismos causais. O clínico deve basear-se nos seguintes fatores: história médica e familiar detalhadas; características da apresentação clínica; biópsias de pele, com análises histológicas e ultraestruturais; e, em alguns casos, se disponíveis, análises bioquímicas. A confirmação do diagnóstico deve ser efetuada por um estudo de genética molecular (nem sempre acessível), com análise de mutações, que serve de suporte para aconselhamento genético do doente e da sua família e possibilita a realização de um diagnóstico pré-natal (em famílias de risco). O tratamento é sintomático uma vez que a doença subsiste, até ao momento, sem cura. Consiste na aplicação contínua de emolientes tópicos, uso de óleos de lavagem para o banho, aplicação de cremes ou pomadas com agentes queratolíticos, remoção mecânica das escamas e utilização de terapia retinóide, um importante avanço na terapêutica destas doenças.
Relativamente a perspetivas futuras, considera-se que um melhor entendimento acerca da patofisiologia das diferentes ictioses contribuirá para o desenvolvimento de estratégias terapêuticas específicas e inovadoras, já que não se afiguram, ainda, perspetivas de descoberta de uma cura.
Ichthyoses are a clinically and etiologically heterogeneous group of skin conditions, classified as disorders of keratinization or cornification. They are the consequence of metabolic defects that result in an abnormal epidermal differentiation, giving the skin a peculiar scaly aspect, reminiscent of fish scales, from which derives the name of the disease (from the Greek ichthys i.e. fish). The purpose of this dissertation is to make a progress report on current knowledge and advances associated with ichthyoses, focusing on a historical perspective to the present day and addressing successively: Classification, Etiology and Pathogenesis, Clinical Presentation, Diagnosis, Therapeutic Strategies and Future Prospects. Ichthyoses have been classified in diverse ways, over time, based on the current knowledge about its etiologic, pathogenic, clinical, histologic, genetic and molecular features. Currently, classification of ichthyoses is based on whether they are the result of a hereditary genetic defect - Hereditary Ichthyoses – or they are the consequence of systemic diseases - Acquired Ichthyoses. Hereditary ichthyoses are subdivided into two major groups, Nonsyndromic Forms (the phenotypic expression of the disorder is only seen in the skin) and Syndromic Forms (a skin condition occurs in association with anomalies in other organs). Nonsyndromic Forms are divided into three major groups: Common Ichthyoses, Autosomal Recessive Congenital Ichthyoses and Keratinopathic Ichthyoses. The genetic causes for most of the 36 types of inherited ichthyoses have been discovered over the last two decades. As for their molecular bases, only a few remain to be identified. Cutaneous alterations associated with ichthyoses are clinically characterized as hyperkeratosis and/or diffuse scaling. Clinical presentation varies not only in severity (ranges from xerosis to life-threatening forms) but also in the age of onset and associated symptoms. Reaching a specific diagnosis may prove difficult given the complex heterogeneity of ichthyoses. The diagnosis should be based on the following data: family and medical history, clinical presentation features, skin biopsies with histological, ultrastructural, and in some cases, biochemical analyses (if available). It should be confirmed by mutation analysis (not always available) to allow for genetic counseling of the patients and their families. It also permits DNA-based prenatal diagnosis in families at risk. Treatment is essencially symptomatic for a cure has not yet been found. It consists on the mechanical removal of the scales, continuous application of topical emollients, bath oils and creams or ointments with keratolytic agents, and retinoid therapy, a significant improvement as the therapeutic field of ichthyoses is concerned. For future perspectives, it is considered that a better understanding of the pathophysiology of the different ichthyoses will contribute to the development of innovative and specific therapeutic strategies, as there are still no perspectives of finding a cure.
Ichthyoses are a clinically and etiologically heterogeneous group of skin conditions, classified as disorders of keratinization or cornification. They are the consequence of metabolic defects that result in an abnormal epidermal differentiation, giving the skin a peculiar scaly aspect, reminiscent of fish scales, from which derives the name of the disease (from the Greek ichthys i.e. fish). The purpose of this dissertation is to make a progress report on current knowledge and advances associated with ichthyoses, focusing on a historical perspective to the present day and addressing successively: Classification, Etiology and Pathogenesis, Clinical Presentation, Diagnosis, Therapeutic Strategies and Future Prospects. Ichthyoses have been classified in diverse ways, over time, based on the current knowledge about its etiologic, pathogenic, clinical, histologic, genetic and molecular features. Currently, classification of ichthyoses is based on whether they are the result of a hereditary genetic defect - Hereditary Ichthyoses – or they are the consequence of systemic diseases - Acquired Ichthyoses. Hereditary ichthyoses are subdivided into two major groups, Nonsyndromic Forms (the phenotypic expression of the disorder is only seen in the skin) and Syndromic Forms (a skin condition occurs in association with anomalies in other organs). Nonsyndromic Forms are divided into three major groups: Common Ichthyoses, Autosomal Recessive Congenital Ichthyoses and Keratinopathic Ichthyoses. The genetic causes for most of the 36 types of inherited ichthyoses have been discovered over the last two decades. As for their molecular bases, only a few remain to be identified. Cutaneous alterations associated with ichthyoses are clinically characterized as hyperkeratosis and/or diffuse scaling. Clinical presentation varies not only in severity (ranges from xerosis to life-threatening forms) but also in the age of onset and associated symptoms. Reaching a specific diagnosis may prove difficult given the complex heterogeneity of ichthyoses. The diagnosis should be based on the following data: family and medical history, clinical presentation features, skin biopsies with histological, ultrastructural, and in some cases, biochemical analyses (if available). It should be confirmed by mutation analysis (not always available) to allow for genetic counseling of the patients and their families. It also permits DNA-based prenatal diagnosis in families at risk. Treatment is essencially symptomatic for a cure has not yet been found. It consists on the mechanical removal of the scales, continuous application of topical emollients, bath oils and creams or ointments with keratolytic agents, and retinoid therapy, a significant improvement as the therapeutic field of ichthyoses is concerned. For future perspectives, it is considered that a better understanding of the pathophysiology of the different ichthyoses will contribute to the development of innovative and specific therapeutic strategies, as there are still no perspectives of finding a cure.
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Keywords
Ictioses Ictioses - Diagnóstico Ictioses - Tratamento Ictioses - Patogenia Ictioses - Etiopatogenia
Pedagogical Context
Citation
Publisher
Universidade da Beira Interior