Sterile alpha motif domain-containing protein 9 is a 1,589-amino-acid protein encoded by the SAMD9 gene. This cytoplasmic protein is a tumor suppressor that has a role in cell proliferation and the innate immune response to viral infection. Like its paralog, SAMD9-like (SAMD9L) protein, its N-terminus contains a sterile alpha motif (SAM). Deleterious mutations of this gene cause normophosphatemic familial tumoral calcinosis (NFTC). On the other hand, mutations that increase the activity of SAMD9 cause myelodysplasia, infection, restriction of growth, adrenal hypoplasia (small adrenal glands with diminished function), genital phenotypes, and enteropathy (MIRAGE) syndrome. This can lead to loss of chromosome 7 as described for monosomy 7 and myelodysplastic syndrome and leukemia syndrome-2 (M7MLS2). Loss of chromosome 7/7q may be an adaptation to a growth restriction inherent in SAMD9/9L mutant cells.