Marfan syndrome (MFS; OMIM no. 154700) is the founding member of connective tissue disorders. It is autosomal dominant and has an estimated incidence of 1 in 5000 with probably over 25% of sporadic cases. The syndrome involves many systems (skeletal, ocular, cardiovascular, pulmonary, skin and integumentary, and dural), but its more prominent manifestations are skeletal, ocular, and cardiovascular. It is characterized by extreme variability in phenotype severity between different affected members of a given family. At least two genes are implicated in MFS: in the majority of cases, mutations in FBN1, the gene encoding fibrillin-1 (the major component of microfibrils), are implicated. Linkage analyses have localized a second gene in 3p24.2-p25. Because no specific clinical anomaly is associated with mutations in each gene, both must be tested for molecular diagnosis.
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The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.