A bone neoplasm characterized by development of two or more cartilage capped bony outgrowths (osteochondromas) of the long bones. The disease is Monarch Disease Ontology id MONDO_0005508 (hereditary multiple osteochondromas). Also known as: Bessel-Hagen disease, exostoses, multiple, multiple cartilaginous exostoses, multiple congenital exostosis, multiple exostosis syndromes, multiple ostechondromas, osteochondromatosis syndrome, osteochondromatosis syndrome (disorder) [ambiguous].