The genetic origin of such dermatoses results in the hereditary nature of the disorder, which means that families and generations may be similarly afflicted. In the last few decades, there has been an explosion of research with the completion of the human genome project in addition to the emergence of array-based methods for linkage analysis and homozygosity mapping. Furthermore, next generation sequencing technology using whole-exome (all transcribed genes) and whole-genome approaches have revolutionized genetic and genomic research. These advances in molecular technology have led to elucidation of the genetic basis of many single-gene inherited skin disorders and have greatly improved our understanding of such conditions. Genotype-phenotype correlations are often complex, with multiple examples of allelic heterogeneity (different mutations in the same gene at the same chromosomal locus causing a single phenotype) and locus heterogeneity (mutations in genes at different chromosomal loci causing the same phenotype).
Disease classification has been simplified by the integration of molecular and clinical data. In recent years, classification systems of several inherited disorders, e.g., epidermolysis bullosa and inherited ichthyosis have been devised by leading authorities. These serve as references for clinicians and researchers.
A detailed family history and pedigree tree are prerequisites in the evaluation of any suspected genodermatosis. It must also be noted that the genetic defect may result from a new mutation or deletion which occurs sporadically. As such, a negative family history does not preclude the diagnosis of a genodermatosis. Polygenic disorders, like atopic dermatosis and psoriasis, are excluded from this category. In the overall management of genodermatoses, the diagnostic evaluation and therapeutic management must be complemented by comprehensive and compassionate genetic counseling on the spectrum of phenotypic expression, prognosis, and potential transmission risk of the disease.
Currently, there are no good population-based epidemiological data on genodermatoses in Asia. Thus, this is a potential area for further research. However, communication with pediatric dermatologists from Thailand, the Phillipines, Indonesia, Sri Lanka, and Malaysia suggests that the following genodermatoses are more commonly seen in South-East Asia:
Autosomal dominant conditions such as ichthyosis vulgaris, neurofibromatosis type 1, Darier’s disease, Hailey-Hailey disease, steatocystoma multiplex, epidermolysis bullosa simplex, tuberous sclerosis, porokeratosis of Mibelli, and autosomal dominant palmoplantar keratoderma
Autosomal recessive conditions such as lamellar ichthyosis and Netherton syndrome
X-linked dominant conditions like incontinentia pigmenti
Heterogeneous conditions like pseudoxanthoma elasticum (which exhibits both autosomal dominant and autosomal recessive inheritance)
Inheritance is usually in an autosomal dominant or autosomal recessive pattern in monogenic genodermatoses, although X-linked dominant and X-linked recessive disorders exist.
Autosomal Dominant Inheritance
In this inheritance pattern, affected individuals are heterozygous carriers of a mutant allele that has been inherited from an affected parent. For the children of an affected individual, the recurrence risk is 50% (one out of two children is expected to be affected). However, cases of ...