Autosomal Recessive

Autosomal recessive

In autosomal recessive inheritance

·         only homozygotes are affected

·         males and females are equally likely to be affected

·         not manifest in every generation - may 'skip a generation'

If two heterozygote parents

·         25% chance of having an affected (homozygote) child

·         50% chance of having a carrier (heterozygote) child

·         25% chance of having an unaffected (i.e. genotypical) child

If one affected parent (i.e. homozygote for gene) and one unaffected (i.e. not a carrier or affected)

·         all the children will be carriers

Autosomal recessive disorders are often metabolic in nature and are generally more life-threatening compared to autosomal dominant conditions

Autosomal recessive conditions

Autosomal recessive conditions are often thought to be 'metabolic' as opposed to autosomal dominant conditions being 'structural', notable exceptions:

·         some 'metabolic' conditions such as Hunter's and G6PD are X-linked recessive whilst others such as hyperlipidaemia type II and hypokalaemic periodic paralysis are autosomal dominant

·         some 'structural' conditions such as ataxia telangiectasia and Friedreich's ataxia are autosomal recessive

The following conditions are autosomal recessive:

·                     Albinism

·                     Ataxia telangiectasia

·                     Congenital adrenal hyperplasia

·                     Cystic fibrosis

·                     Cystinuria

·                     Familial Mediterranean Fever

·                     Fanconi anaemia

·                     Friedreich's ataxia

·                     Glycogen storage disease

·                     Haemochromatosis

·                     Homocystinuria

·                     Lipid storage disease: Tay-Sach's, Gaucher, Niemann-Pick

·                     Mucopolysaccharidoses: Hurler's

·                     PKU

·                     Sickle cell anaemia

·                     Thalassaemias

·                     Wilson's disease