The horn: a pathognomonic feature of paediatric bone dysplasias.

In conclusion, this brief communication has summarized two fascinating systemic syndromes with the unusual common feature of a pathognomonic radiographic sign. In osteo-onychodysostosis, characteristic osseous horns arise from the posterior iliac wings, whereas in Type IX Ehlers-Danlos syndrome, similar protuberances extend inferiorly from the occiput. Although both conditions are uncommon, an awareness of these horns as specific earmarks of each is important, since early diagnosis may allow preventive intervention for their serious potential complications later in life.