Bifid rib

A bifid rib is a congenital abnormality occurring in about 1% of the population. The sternal end of the rib is cleaved into 2. It is usually unilateral.

Usually it is clinically silent but it may present as a coincidental finding on chest radiography when there appears to be 8 vertebrae articulating with the sternum.

Note that very rarely a bifid rib may occur as part of Gorlin-Goltz syndrome (1) or Jobs syndrome (2). It also has been reported as occurring in Kindler syndrome (3).

Reference:

1. D.G.R. Evans, P.A. Farndon, L.D. Burnell et al., The incidence of Gorlin syndrome in 173 consecutive cases of medulloblastoma. Br J Cancer 64 (1991), pp. 959–961
2. J Chinen et al. Skeletal anomalies in hyper-IgE recurrent infection syndrome (HIES, Job syndrome). Journal of Allergy and Clinical Immunology, Volume 113, Issue 2, Supplement 1, February 2004, Page S46
3. Sharma JC et al. Kindler syndrome. Int J Dermatol. 2003 Sep;42(9):727-32.