Multifactorial inheritance

Many common diseases exhibit multifactorial inheritance. 

Fearnhead NS, Wilding JL, Winney B, Tonks S, Bartlett S, et al. 2004. Multiple rare variants in different genes account for multifactorial inherited susceptibility to colorectal adenomas. Proc Natl Acad Sci USA 101 15992-15997. 

Diabetes mellitus (DM) is a metabolic carbohydrate disorder that results from either insufficient insulin (type 1 DM) or the body s inability to recognize available insulin (type 2 DM). DM is a multifactorially inherited disorder this means that although people can inherit a propensity toward this condition, environment and diet can trigger onset of the actual disease. People who suffer from DM experience abnormally high blood... 

Which phrase best defines the genetic disease category of multifactorial inheritance ... 

Possible autosomal dominant inheritance or multifactorial inheritance of cancer predisposition... 

Unstable trinucleotide repeats Multifactorial inheritance Mitochondrial inheritance... 

The answer is a. (Murray, pp 812-828. Scriver, pp 3-45. Sack, pp 167—180. Wilson, pp 287-324.) When present as an isolated anomaly, spina bifida (meningomyelocele) exhibits multifactorial inheritance. Chromosomal inheritance usually causes a syndrome rather than isolated anomalies. Atypical inheritance (genomic imprinting, trinucleotide repeat instability, mitochondrial inheritance) has not been implicated in neural tube defects. 

Motulsky, A. G. (1978) Multifactorial inheritance and heritability in pharmacogenetics. Human Genet. 44, (Suppl 1), 7-11. 

After birth of a child with severe Potter phenotype due to bilateral agenesis or dysplasia in up to 10% unilateral agenesis or dysplasia can be found in one parent indicating a genetic basis. Empirical recurrence risks favour mostly multifactorial inheritance with a recurrence risk of about 5% after birth of a child with renal agenesis/dysplasia. In single pedigrees, autosomal dominant or X-linked mode of inheritance seems to be likely with incomplete penetrance and variable expressivity. Specific syndromes have to be ruled out (Table 3.2). 

A genetic basis is well known, many reported families indicate autosomal dominant inheritance with variable expressivity and incomplete penetrance. In about 10% of parents and siblings similar observations can be made, indicating multifactorial inheritance for the majority of cases. According to the general rule of thumb, the recurrence risk doubles with each additionally affected close relative. Isolated duplication anomalies have to be distinguished from genetic syndromes (Table 3.5). 

Although autosomal dominant inheritance has been postulated, the risk among close relatives of affected people is about 20%, indicating either poor penetrance, multifactorial inheritance, or an admixture of nongenetic causes. 

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