OBJECTIVE: This work evaluates the potential presence of bone disease in an extinct primate from late Pleistocene of Brazil. MATERIALS: The skull and post crania of an extinct platyrrhine primate, curated by the Museu de Ciências Naturais PUC, Brazil. METHODS: Pathological changes were noted via analysis of radiographic images and CT of the affected bones. RESULTS: The lesions noted include cortical thickening, sclerosis, and coarse trabeculae in the skull and long bones. CONCLUSIONS: The features observed support the diagnosis of metabolic bone disease with lesions comparable to those seen in Paget's disease. SIGNIFICANCE: This specimen appears to be the only case is of metabolic bone disease in an extinct New World monkey and adds data to the paleopathological record of South American primates. LIMITATIONS: The absence of other skeletal materials from individuals of the same genus for comparison makes differential diagnosis challenging, and conclusions must be drawn with caution. SUGGESTIONS FOR FURTHER RESEARCH: A more complete comparative sample of images involving more genera of living and extinct platyrrhines can help to rule out morphological oddities and design a more accurate diagnosis.