LOOKING BACK: THROUGH PRESENT LIGHT
Year : 2006 | Volume
: 51 | Issue : 1 | Page : 73-
The inheritance of susceptibility to lichen planus
M Hafez, L Sharaf, FA Seafan
The role of inheritance of susceptibility in lichen planus was studied by genetic analysis of data from 71 families of probands with lichen planus. 12 families were multiplex and the other 59 were simplex. The incidence of the disease among relatives of probands was significantly higher than that in the general population and the frequency diminished with the descend in the degree of relationship between relatives and probands. Pedigrees of the families of probands did not consist of any single-gene inheritance.
The results shown by the curve of liability of the relatives, the frequency in the first degree relatives and the relative frequency points to a polygenic-environmental interaction.
The heritability of liability for lichen planus which measures the relative contribution of genetic factors in etiology was found to be 56 percent for first-degree relatives.
The etiology of lichen planus is still not properly known. Several pathogenetic theories have been proposed despite limited supportive evidences. The main theories are: infective, autoimmune, psychogenic and genetic.
The aim of this work is to throw a beam of light on the genetic role in the pathogenesis of lichen planus.
|How to cite this article:|
Hafez M, Sharaf L, Seafan F A. The inheritance of susceptibility to lichen planus.Indian J Dermatol 2006;51:73-73
|How to cite this URL:|
Hafez M, Sharaf L, Seafan F A. The inheritance of susceptibility to lichen planus. Indian J Dermatol [serial online] 2006 [cited 2020 Jul 9 ];51:73-73
Available from: http://www.e-ijd.org/text.asp?2006/51/1/73/25220
This is a remarkable study in clinical genetics on a subject that is still ill-understood. In order to evaluate the significance of the study, however, it has to be judged in the proper historical context, particularly when a few of its contentions have been overturned in the light of later scientific understanding.
The current consensus in lichen planus (LP) studies is that familial cases are uncommon and certainly the frequency of hereditary susceptibility is nowhere near the figure that was arrived at in this study. Still, it has to be considered that, for genetic analysis, this work had only clinical evidence and pedigree construction to depend upon. The genetic hypotheses, upon which the segregation analysis was predicated, were elegant yet simplistic, based as they were on human heredity theories propounded in the fifth decade of the last century.
The fact is that in those early years of eighties, human leukocyte antigen (HLA) studies had only recently come into being. Advances in immunology and molecular genetics including, inter alia, introduction of the Southern Blot technique, the polymerase chain reaction (PCR), immunophenotyping and genomic DNA studies, that have revolutionized the diagnosis of cutaneous lymphocytic infiltrates, had yet to come into currency.
The convergence and interpenetration of immunology and genetics was not established, so that phenomena such as close chromosomal proximity of major histocompatibility complex (MHC) and tumour necrosis factor (TNF) genes were not even thinkable propositions. Consequently, studies that make use of such phenomena (e.g, one that examines the -308 promoter polymorphism of TNF gene in LP patients using an allele-specific PCR to seek a correlation between genotypic distribution, allele frequency etc.) could not even be conceived of at that juncture.
It is a tribute to the authors of this study that at least two of their major conclusions regarding the pathogenicity and heritability of LP, polygenic-environmental interaction and multifactorial inheritance, remain largely inviolate. This is all the more creditable in view of two facts: One, the authors could arrive at such correct conclusions even when working with familial cases; and, two, in the eighties the Mendelian genetic theory of susceptibility of LP (as also of several other conditions) held much greater sway than it does today.
No doubt, the greatest strength of the study was its sample size. The number of families of probands (n=71) with LP in this study outstrips by far any of the contemporary studies of familial LP, even much more well-known ones, those that are oft-quoted even to this day. Perhaps this fact, combined with the honest, no-nonsense approach, lends to the significance and credibility of the study. This article by Hafez et al deserves to be treated as a landmark in the annals of clinical research of lichen planus.
Associate Editor, IJD
|1||Holm N, Flaig MJ, Yazdi AS, Sander CA. The value of molecular analysis by PCR in the diagnosis of cutaneous lymphocytic infiltrates. J Cutan Pathol 2002, 29(8); 447-52.|
|2||Krasowska D, Chodorowska G, Koziol-Montewka M, Ksiazek A, Buraczynska M. The -308 promoter polymorphism in the tumour necrosis factor gene in patients with lichen planus. Acta Derm Venereol 2005, 85(5); 400-3.|
|3||Mahood JM. Familial lichen planus. A report of nine cases from four families with a brief review of the literature. Arch Dermatol 1983, 119; 292-4.|