The button sequestrum sign is demonstrated in a number of medical conditions and refers to a lesion of devascularised bone which is surrounded by lucency. Although it may be difficult to arrive at a single diagnosis based on this sign, the combination of clinical and paraclinical findings, patient's medical history and imagistic presentation of this sign can lead to a great specificity in chronic osteomyelitis, even if osteomyelitis is accompanied by osteopetrosis, as in the present case.