Peritonsillar abscess
A collection of pus between the tonsil capsule and the pharyngeal muscles (quinsy), forming when tonsillitis spreads beyond the tonsil into an adjacent tissue plane, producing trismus and a muffled voice that mark it out as a surgical emergency rather than severe tonsillitis.
First principles
The peritonsillar space is a potential space that infection can track into
The tonsil is separated from the surrounding pharyngeal constrictor muscles by a thin capsule and a potential space containing loose connective tissue and small mucous (Weber's) glands. In severe or inadequately treated bacterial tonsillitis, infection can breach the tonsil capsule and spread into this adjacent space, where pus then accumulates because the space offers little resistance to collection once infection establishes there. This is the key mechanistic difference from tonsillitis: the infection is no longer confined to lymphoid tissue but has become a collection of pus in a separate anatomical compartment, which is why it needs drainage rather than antibiotics alone.
Educational content pending clinical review. Not medical advice.