Rare Presentation of Parsonage-Turner Syndrome Post Tdap Vaccination: A Case Report.

Parsonage-Turner Syndrome (PTS) is a rare disorder of the brachial plexus typically characterized by acute shoulder and/or upper extremity pain, followed by muscle weakness. Though the specific etiology of PTS is unclear, numerous associations are cited in the literature, including after routine vaccinations. A previously healthy 22-year-old male developed subacute left upper extremity weakness and numbness < 24 hours following a routine Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis) booster vaccination, later evolving into diffuse weakness and sharp shoulder pain. Electromyography (EMG) findings were suggestive of early PTS, and subsequent magnetic resonance imaging (MRI) of the brachial plexus confirmed mild inflammatory changes consistent with brachial plexitis. Over several months, the patient showed clinical improvement with conservative management. This case highlights a rare presentation of post-vaccination PTS, emphasizing the need for early recognition and supportive management. Although rare, clinicians should consider PTS in patients presenting with acute-onset upper extremity pain and weakness following vaccination.