[Costal exostoses, complicated in the neonatal period, by brachial plexus paralysis. A distinct entity of exostoses?].

Two highly unusual cases of brachial plexus palsy due to compression by exostosis of the first rib in the neonatal period are reported. Etiologic diagnosis in these patients required elimination of other tumors of the first rib, including multiple exostoses. The contradictions found lead the authors to suggest individualization of a form of multiple exostoses different from classical multiple exostoses by a number of features including growth, complications, and inheritance. At present, it is not known whether this new entity carries the same risk of malignant transformation as classical multiple exostoses.