Inheritance & Autosomal Recessive
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The overall prevalence of Gaucher disease is low,1 occurring at a frequency of approximately 1 in 50,000 to 1 in 100,000 live births.2 Over 90% of patients with Gaucher disease are Type 1.2 However, Type 1 is still rare, and only occurs in about 1 in 30,000 to 1 in 40,000 people in the general population, and due to consanguinity.1 Epidemiology studies have shown that the incidence of the disorder is much higher among Ashkenazi Jews (those of Eastern European origin), with an incidence of 1 in 855 Ashkenazi Jewish births and an estimated carrier frequency of 1 in 18 people.3 In contrast, Types 2 and 3 have a very rare incidence, and occur in less than 1 in 100,000 of the general population.1
1. MEHTA, A. Eur J Int Med. 2006;17:S2–S5.
2. NICE: National Institute for Health and Care Excellence Final scope for the highly specialised technology evaluation of eliglustat for treating type 1 Gaucher disease Issue Date: September 2014 Appendix B
3. PASTORES, GM and HUGHES, DA. Gaucher Disease. 2000 Jul 27 [Updated 2015 Feb 26]. In: Pagon RA, Adam MP, Ardinger HH, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993–2015. http://www.ncbi.nlm.nih.gov/books/NBK1269/.
[Accessed July 2015].
Gaucher disease results from defects in β-glucocerebrosidase function, which is encoded for by the GBA1 gene.1 More than 350 different mutations in the GBA1 gene have been identified, including single nucleotide substitutions (point mutations), substitutions, insertions, deletions, and rearrangements.2,3 Despite the large number of gene mutations identified, the majority of cases of Gaucher disease result from several common GBA1 gene mutations.3,4
Gaucher disease is an autosomal recessive disorder as the mutated GBA1 gene is located on chromosome 1 (an autosomal chromosome, not X or Y) and is only expressed in homozygotes (where both alleles are coding for defective glucocerebrosidase).4 As a result males and females are equally affected by Gaucher disease due to its autosomal recessive nature.
If both parents are carriers of Gaucher disease there is a 1 in 4 (25%) probability that their children will inherit two copies of the mutated Gaucher disease gene (a), and will develop Gaucher disease.
If only one parent is a carrier, there is no possibility of the child having Gaucher disease. However, there is a 1 in 2 (50%) probability that the child will be a carrier.
The pattern of inheritance of a single-gene disorder depends on whether the gene affected is on a sex chromosome or an autosomal chromosome (any non-sex chromosome).1,2 Autosomal disorders relate to genes on autosomal chromosomes, i.e. are not carried by the X or Y chromosome.1,2 The pattern of inheritance also depends on whether the affected gene is expressed as a dominant or recessive trait. A recessive trait is expressed only in homozygotes for that gene (i.e. carries 2 copies of the mutated gene).
Therefore, autosomal recessive disorders relate to genes on an autosomal chromosome that are only expressed in homozygotes. For Gaucher disease, this means that a child must inherit the recessive mutated GBA1 gene from both parents to develop the disease.1 A person with Gaucher disease, therefore, has two copies of the mutated gene, whereas a person with one dominant and one recessive gene is defined as a carrier.