ENPP1 and hypopigmentation-punctate palmoplantar keratoderma syndrome: Variants in the ENPP1 gene have been linked to abnormal calcification of soft and skeletal tissues in ectopic mineralization disorders, which include GACI, Cole disease, autosomal recessive hypophosphatemic rickets type II (ARHR2), and ossification of the posterior longitudinal filament of the spine (OPLL) [15,16].