Other Genetic Disorders

Traditional genetics has been extended by the introduction of several new non‐Mendelian concepts of importance in dermatology. Some of these concepts are: mosaicism, contiguous gene deletions, genomic imprinting, uniparental disomy and mitochondrial mutations. Two other important genetic concepts are clinical heterogeneity (when clinically distinct phenotypes are produced by different mutations within the same gene, such as red hair variants caused by different polymorphisms of the MC1R gene) and genetic heterogeneity. This chapter discusses the following genetic disorders of the skin: neurofibromatoses, tuberous sclerosis, xeroderma pigmentosum, incontinentia pigmenti, Ehlers–Danlos syndrome, and pseudoxanthoma elasticum. For each disease, the cause, diagnosis, and management/treatment are presented.