A 26-year-old white man had a painful callus of the lateral area of the right thumb, which was associated with a phalangeal exostosis. This rarely reported entity on the hand probably represents an osteocartilaginous outgrowth from the underlying bone.
Bennett RG, Gammer S. Painful Callus of the Thumb Due to Phalangeal Exostosis. Arch Dermatol. 1973;108(6):826-827. doi:10.1001/archderm.1973.01620270048012