Inheritance
Perinatal and infantile A rare, inherited, and sometimes fatal metabolic bone disease characterized by poor bone mineralization and profound skeletal defects.hypophosphatasia are inherited as A mode of genetic inheritance in which the phenotypic expression of a gene of interest requires its presence on both paired autosomal (non-sex determining) chromosomes.autosomal recessive traits with The presence of identical alleles of a gene on both homologous chromosomes.homozygosity or A genetic term for having two heterogeneous recessive alleles at a particular locus that can result in disease. Because the mutations involved are less deleterious than that in a homozygous individual, compound heterozygotes frequently become ill later in life and display less severe symptoms.compound heterozygosity for two defective TNSALP One of two or more alternate forms of a gene that resides on a specific site (also known as a locus) on a chromosome.alleles. The mode of inheritance for childhood, adult, and odonto forms of hypophosphatasia can be either A mode of genetic inheritance in which the presence of only one copy of a gene that resides on an autosomal (non-sex determining) chromosome will result in phenotypic expression of that gene.autosomal dominant or recessive. Autosomal transmission accounts for the fact that the disease affects males and females with equal frequency. Genetic counseling is complicated by the disease’s variable inheritance pattern31 ; the existence of the rare prenatal benign form, and by incomplete penetration of the trait32.
Autosomal Dominant
Autosomal Recessive
Prevalence
HPP is a rare disease that has been reported worldwide and appears to affect individuals of all ethnicities33.
The prevalence of severe hypophosphatasia is estimated to be 1:100,000 in a population of largely Anglo Saxon origin34. The frequency of mild HPP is more challenging to assess because the symptoms may escape notice, or be misdiagnosed. The highest incidence of HPP has been reported in the Mennonite population in Manitoba, Canada where one in every 25 individuals are considered carriers and one in every 2,500 newborns manifests severe disease35.
HPP is considered particularly rare in people of African ancestry in the U.S.36.