<p>Mulvihill-Smith Syndrome (MSS) is a clinically complex and genetically unsolved nano-rare disorder with only 12 patients reported in the literature. Most patients (91%) have immunological impairments, succumb to infection, and might develop cancer later in life. Its pathogenesis remains elusive and therapeutic options are limited. We used single-cell MULTI-omics (sc-MULTI-omics), combining transcriptomics (gene expression, TCR, and BCR repertoire) and proteogenomic (Cellular Indexing of Transcriptomes and Epitopes by Sequencing; CITE-seq), to decipher the pathophysiology of nano-rare disease patient. We report a new patient who is a 16-year-old girl. She had an increased leukocyte counts and typical manifestations of MSS such as short stature, older appearance, multiple pigmented nevi, microcephaly, monolateral keratoconus, Marcus-Gunn syndrome, hearing loss, vitamin D deficiency, mild hypercortisolism, and diabetes mellitus with very high insulin resistance (T3DM). sc-MULTI-omics CITE-seq showed that the MSS patient had increased central memory CD4⁺ T cells as well as effector memory CD8⁺ T cells, whilst reduced naïve T cells (both CD4⁺ and CD8⁺ T cells). Furthermore, we identified genes and pathways associated with the progeria-like phenotype, inflammation, and cancer progression, which may contribute to the clinical signs of MSS. sc-MUTLI-omics CITE-seq analyses improve our understanding of complex human disease pathophysiology and provides an alternative approach in personalized medicine in nano-rare disease.</p> Graphical abstract <p></p>