Interferon-stimulated gene 15 (ISG15) was the first ubiquitin-like modifier protein identified that acts by protein conjugation (ISGylation) and is thought to modulate IFN-induced inflammation. Here, we report a new patient from a non-consanguineous Argentinian family, who was followed for recurrent ulcerative skin lesions, cerebral calcifications and lung disease. Whole Exome Sequencing (WES) revealed two novel compound heterozygous variants (c.285del and c.299_312del, NM_005101.4 GRCh37(hg19), both classified as pathogenic according to ACMG criteria) in the ISG15 gene, resulting in a complete deficiency due to disruption of the second ubiquitin domain of the corresponding protein. The clinical phenotype of this patient is unique given the presence of recurrent pulmonary manifestations and the absence of mycobacterial infections, thus resulting in a phenotype distinct from that previously described in patients with biallelic loss-of-function (LOF) ISG15 variants. This case highlights the role of ISG15 as an immunomodulating factor whose LOF variants result in heterogeneous clinical presentations.