Abstract

Post-streptococcal reactive arthritis (PSRA) is associated with a prior group A streptococcal infection and has a bimodal age distribution. Clinical features of arthritis caused by PSRA, including symmetric or asymmetric, usually non-migratory, can affect any joint, persistent or recurrent, and the sacroiliac joint is most affected in Asia. Congenital lumbosacral malformation including transitional vertebrae or spina bifida occulta, is one of the etiologies of lower back pain. However, the congenital absence of the fifth lumbar vertebra with lower back pain has not been reported yet. We present a case of a 28-year-old man having only four lumbar vertebrae, who was ultimately diagnosed with PSRA involving the SI joints. We assumed that his lower back pain is not solely due to PSRA, the absence of the fifth lumbar vertebra also plays an important role. A detailed description of these two mechanisms which may contribute to his symptom was discussed in the text

Keywords

sacroiliitis, post-streptococcal reactive arthritis, anti-streptolysin o, quantitative sacroiliac scintigraphy, whole body bone scan, single photon emission computed tomography – computed tomography, scintigraphic rehabilitation