Idiopathic infantile arterial calcification (IIAC; OMIM 208000) is characterized by calcification of the internal elastic lamina of muscular arteries and stenosis due to myointimal proliferation. We analyzed affected individuals from 11 unrelated kindreds and found that IIAC was associated with mutations that inactivated ecto-nucleotide pyrophosphatase/phosphodiesterase I (ENPP1). This cell surface enzyme generates inorganic pyrophosphate (PPi), a solute that regulates cell differentiation and serves as an essential physiologic inhibitor of calcification.
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We thank H. Ritter for microsatellite analyses; I. Bäβmann for technical assistance in cell culturing and mRNA preparation; and D. Morris, N. Makhseed and E. Harps for providing material from affected individuals. This work was supported in part by grants from the Deutsche Forschungsgemeinschaft (F.R., P.N.), the German Federal Department of Education and Research (P.N.), the US National Institutes of Health and Veterans Affairs Research Service (R.T.) and the US Arthritis National Research Foundation (S.V.).