Is Hypophosphatasia inherited ?
How is hypophosphatasia inherited? Perinatal (onset before birth) and infantile hypophosphatasia (HPP) are inherited in an autosomal recessive manner. This means that to be affected, a person must have a mutation in both copies of the responsible gene (ALPL) in each cell. Affected people inherit one mutated copy of the gene from each parent, who is referred to as a carrier. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When 2 carriers of an autosomal recessive condition have children, each child has a: 25% (1 in 4) chance to be affected 50% (1 in 2) chance to be an unaffected carrier like each parent 25% chance to be unaffected and not be a carrier. The milder forms, especially adult HPP and odontohypophosphatasia, may be inherited in an autosomal recessive or autosomal dominant manner - depending on the effect the ALPL mutation has on enzyme activity. In autosomal dominant inheritance, having a mutation in only one copy of the ALPL gene in each cell is enough to cause features of the condition. When a person with a mutation that causes an autosomal dominant HPP has children, each child has a 50% (1 in 2) chance to inherit that mutation. Most people with autosomal dominant HPP have inherited the mutation from a parent who may or may not have symptoms. Not all people with a mutation that causes autosomal dominant HPP develop symptoms of the condition. While it is possible to have autosomal dominant HPP due to a new mutation that was not inherited (a de novo mutation), this has never been reported in HPP.