<prompt> The sign marked by the arrows pointing to the ribs, in the below chest X-ray, is diagnostic of which of the following conditions?HyperthyroidismChronic renal failureCoarctation of aortaMultiple myeloma  <response>: Ans. C. Coarctation of aortaThe above chest X-ray shows, inferior rib notching Roesler sign, which is characteristically seen in patients with coarctation of aorta.Aortic coarctation, or Coarctation of aorta is a congenital condition whereby the aorta is narrow, usually in the area where the ductus arteriosus ligamentum arteriosum after regression inserts. Three important findings are: Inferior rib notching Figure 3 sign of the aorta Prominence of the ascending aortaInferior rib notching Roesler sign: The most common cause is coarctation of aorta, however certain other conditions as follows may cause inferior rib notching: Takayasu disease Blalock-taussig shunt Arteriovenous malformation SVC obstruction Certain neurogenic tumors like schwannomaBoth superior and inferior rib notching may be seen in: Hyperparathyroidism Neurofibromatosis type 1 