A patient presents with unilateral tonsillar swelling and pyrexia. What is the likely condition?

The presence of unilateral tonsillar swelling combined with pyrexia suggests an acute condition that often involves the tonsils specifically. Quinsy, also known as peritonsillar abscess, typically arises as a complication of tonsillitis. This condition is characterized by the accumulation of pus in the area adjacent to the tonsil, leading to significant swelling, pain, and difficulty swallowing. Additionally, patients often present with a fever, which aligns with the pyrexia noted in the scenario.

While tonsillitis can present with bilateral tonsillar swelling and fever, the unilateral aspect and the severity of symptoms point more towards quinsy. Pharyngitis and laryngitis primarily involve inflammation of the pharynx and larynx, respectively, and do not typically cause significant unilateral tonsillar swelling or the same severity of systemic symptoms as observed in this case. Thus, considering the clinical features presented, peritonsillar abscess is the most likely diagnosis.