In clinical practice and literature studies, the most common condition associated to streptococcal tonsillitis used to be acute rheumatic fever (ARF). Several publications in the late years report a more frequent and distinctive entity from ARF following β-hemolytic group A streptococcus infection in patients with post-infectious arthritis, that do not fulfill the modified Jones criteria, the so-called post-streptococcal reactive arthritis (PSRA). A distinctive pattern of clinical framing and biological profile in patients with PSRA following streptococcal tonsillitis is described, with a non-migratory, additive, recent onset (7-10 days) arthritis that affects small and large joints as well, with a bimodal peak of incidence at 8-14 and 21-37 years of age, with variate response to non-steroidal anti-inflammatory drugs and has a tendency for recurrence and persistence. Sacroiliitis, although rare, is described in human leukocyte antigen (HLA)-B27 positive PSRA patients. The main objective of the current study was to evaluate various immunohistochemical patterns of streptococcal tonsillitis in patients with PSRA and find possible correlations with the clinical, biological and ultrasound profile.