- Familial hypercatabolic hypoproteinemia caused by deficiency of the neonatal Fc receptor, FcRn, due to a mutant beta2-microglobulin gene. Wani, M.A., Haynes, L.D., Kim, J., Bronson, C.L., Chaudhury, C., Mohanty, S., Waldmann, T.A., Robinson, J.M., Anderson, C.L. Proc. Natl. Acad. Sci. U.S.A. (2006)