FOP is a gain-of-function disease that results from a mutation in the ACVR receptor. This cartoon highlights some of the known signaling pathways involved in FOP. As shown, the mutated ACVR1 (ALK2) receptor sits across a cell’s membrane. Ligands (Activin A, BMPs) bind to the receptor causing the FOP receptor to turn on and transmit signals inside the cell. The mutant ACVR1 receptor sends incorrect signals (i.e. make more bone) to the cell's nucleus.

Several therapeutic approaches are being tested in FOP, which target various stages of the signaling pathway (highlighted in yellow). To learn more, hover your cursor over the “i” shown in the diagram.