Progeria syndromes are rare disorders that involve premature aging. Mutations in BANF1 have been recently reported to cause a new hereditary progeroid syndrome that we now propose to call the Néstor–Guillermo progeria syndrome (NGPS). We describe herein the clinical features of the first two NGPS patients, who phenocopy features of classic progerias (i.e., Hutchinson–Gilford progeria syndrome or mandibuloacral dysplasia), such as aged appearance, growth retardation, decreased subcutaneous fat, thin limbs, and stiff joints. However, these NGPS patients have a distinctive phenotype. In their early adulthood (32 and 24 years of age), they have no signs of cardiovascular impairment, diabetes mellitus, or hypertriglyceridemia. In contrast, they suffer profound skeletal abnormalities that affect their quality of life. The observed differences are of utmost importance to patients and their families and palliation of osseous manifestations is a priority, given their relatively long lifespan. We define NGPS as a chronic progeria because of its slow clinical course and relatively long survival, despite its early onset. Understanding the differences between progeria syndromes might contribute to the development of treatment strategies for common skeletal conditions, as well as aging itself. © 2011 Wiley Periodicals, Inc.