Introduction

Genetically determined chromosomal instability was first discovered in Bloom syndrome (BS), a clinical entity that is now known to be the result of mutations in the recQ gene BLM. The RecQ proteins are a large family of evolutionarily conserved DNA helicases, which are enzymes that unwind double-stranded DNA (ds-DNA), and they function in ways not completely understood in the maintenance of genomic stability (1). In all biological systems studied so far, mutations in the recQ helicase genes result in various genomic instabilities that are detectable at both the level of the chromosomes and the genomic DNA. In humans, there are five recQ genes, three of which are associated with human diseases, namely BS, Werner syndrome (WS), and Rothmund-Thomson syndrome (RTS). A comparison of the clinical and genetic features of these three syndromes is presented in Table 1. WS results from mutations in the recQ helicase WRN, and it is most remarkable clinically for the development prematurely of features of aging (see Chapter 9). Consequently, WS has served as a model for understanding the aging process.

BS is a rare autosomal recessive disorder first recognized as a clinical entity by the New York dermatologist David Bloom, who brought together three children affected by growth deficiency with normal proportions and a sun-sensitive, telangiectatic facial erythema that resembled lupus erythematosus (2). Since this initial description of BS, a number of other features of the entity have become apparent, including a characteristic facies and voice, hypopigmented and hyerpig-

Table 1 Comparison of the Clinical Features of the Syndromes in Which RecQ Helicases Are Known to Be Defective

Syndrome

Major clinical features

Cancer diathesis

Cytogenetic findings

Bloom syndrome

Small size, sun-sensitive

All types, including

Isochromatid breaks

How To Deal With Rosacea and Eczema

How To Deal With Rosacea and Eczema

Rosacea and Eczema are two skin conditions that are fairly commonly found throughout the world. Each of them is characterized by different features, and can be both discomfiting as well as result in undesirable appearance features. In a nutshell, theyre problems that many would want to deal with.

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