Nora’s Lesion: A Rare Tumor in the Pediatric Population

Nora’s lesion or bizarre periosteal osteochondromatous proliferation, first described by Nora in 1983 [1], is a very rare condition with only about 160 cases being described in the literature since then [2,3]. It is more common in adults, in their third to fourth decade [1,2,4] and occurs mostly on the proximal and middle phalanges, metacarpal and metatarsal bones [5]. The etiology of this lesion remains unknown. Some authors hypothesized that traumatic events could be on the origin of it [6]. However, actually there is no evidence of a relationship between trauma and bizarre periosteal osteochondromatous proliferation. Radiologically, it appears as a calcified mass attached to the bone cortex [1] and can mimic an exostosis, an osteochondroma or a malignant condition [7].