IFNA1 and calcification: A defect in USP18-mediated attenuation of type I IFN response has been shown in patients with ISG15 deficiency, a disease characterized by intracranial calcifications, seizures, atypical mycobacteria infection susceptibility, autoantibodies and increased IFN-α or increased expression of IFN stimulated genes in peripheral blood, a biomarker known as type I IFN signature, detected by standard real-time PCR or micro-array technique [33].