Case Report: Acute Additive Polyarthritis as a Presentation of Type 2 Lepromatous Reaction: The Role of Differential Diagnosis.

Introduction: Type 2 lepromatous reaction is a severe complication triggered by proinflammatory cytokines, it affects patients with lepromatous leprosy and border lepromatous leprosy. This reaction can occur before, during, or after treatment.

Case Report: We report a case of acute polyarthritis as type 2 lepromatous reaction debut. A 30-year-old male with a history of Hansen's disease 5 years ago received a complete therapeutic regimen with cure criteria. Consulted due to a 3-day history of arthralgia predominantly affecting the hands, knees, and feet. On the fifth day of hospitalization, the patient developed intensely painful, nodular erythematous lesions. The pathological history, clinical presentation, and the presence of polymorphonuclear cells led to the diagnosis of type 2 lepromatous reaction.

Conclusion: Identifying individuals with risk factors or a history of leprosy, along with a high index of suspicion, positively impacts the early identification of leprosy reactions as an imitator of other causes of acute or chronic symmetrical polyarthritis.