What are the genetic changes related to Mabry syndrome ?
Mutations in the PIGV, PIGO, or PGAP2 gene cause Mabry syndrome. These genes are all involved in the production (synthesis) of a molecule called a glycosylphosphosphatidylinositol (GPI) anchor. This molecule is synthesized in a series of steps. It then attaches (binds) to various proteins and binds them to the outer surface of the cell membrane, ensuring that they are available when needed. Alkaline phosphatase is an example of a protein that is bound to the cell membrane by a GPI anchor.  The proteins produced from the PIGV and PIGO genes are involved in piecing together the GPI anchor. After the complete GPI anchor is attached to a protein, the protein produced from the PGAP2 gene adjusts the anchor to enhance the anchor's ability to bind to the cell membrane.  Mutations in the PIGV, PIGO, or PGAP2 gene result in the production of an incomplete GPI anchor that cannot attach to proteins or to cell membranes. Proteins lacking a functional GPI anchor cannot bind to the cell membrane and are instead released from the cell. The release of non-GPI anchored alkaline phosphatase elevates the amount of this protein in the blood, causing hyperphosphatasia in people with Mabry syndrome. It is unclear how gene mutations lead to the other features of Mabry syndrome, but these signs and symptoms are likely due to a lack of proper GPI anchoring of proteins.  PIGV gene mutations are the most frequent cause of Mabry syndrome, accounting for approximately half of all cases. Mutations in the PIGO and PGAP2 genes are responsible for a small proportion of Mabry syndrome. The remaining affected individuals do not have an identified mutation in any of these three genes; the cause of the condition in these individuals is unknown.