The purpose of this prospective registry is to characterize the natural history of ectonucleotide pyrophosphatase/phosphodiesterase1(ENPP1) Deficiency and the infantile-onset form of adenosine triphosphate (ATP) binding cassette transporter protein subfamily C member 6 (ABCC6) Deficiency longitudinally. The registry will prospectively gather information about the genetic, biochemical, physiological, anatomic, radiographic, and functional manifestations (including patient reported outcomes [PROs]) of each disease during routine, standard-of-care visits, with the aim of developing a comprehensive understanding of the burden of illness and progressive nature of the disease.