Diseases that culminate into vertebral collapse are of intricate diagnosis both in palaeopathology and modern clinical practice. When analysing human skeletal remains from the archaeological record this difficulty is amplified due to the absence of complementary medical diagnostic information. This is especially evident when the distinction between tuberculous and pyogenic spondylitis is intended. Taking into consideration this challenging task and based on the macroscopic and radiological study of the skeleton number 8, a specimen exhumed from the East necropolis (13th/14th to 19th centuries) of the Sã o Miguel church, at the Portuguese city of Castelo Branco, the aims of the work here presented are to discuss the range of possible aetiological factors, especially infectious ones, ascribable to the striking pathological changes noticed on this 12-year-old individual. These included alterations on the axial skeleton, namely extensive vertebral destruction, presenting as a gibbus deformity, and correlated thoracic deformities. Consubstantiated on palaeopathological and clinical research, tuberculous spondylitis seems to be the most probable cause for the reported lesions. However, the scrutiny between this condition and other pyogenic spinal infections is of extreme complexity when analysing ancient human remains and deserves in-depth future investigations. Within the framework of the Portuguese archaeological record, the specimen here presented is of major relevance since the pattern and severity of the spinal osseous changes observed were not previously reported. Further, if tuberculous spondylitis is assumed as the most probable diagnosis, the case here presented represents one of the earliest skeletal evidence of this condition in Portugal.