[A man with painful shins].

Area of Science:

• Rheumatology
• Infectious Diseases
• Dermatology

Background:

• Syphilis is a sexually transmitted infection caused by *Treponema pallidum*.
• Secondary syphilis can present with a wide range of systemic manifestations.
• Periostitis is an inflammation of the bone membrane, often causing bone pain.

Observation:

• A 55-year-old man presented with a 6-week history of painful shins and a maculopapular rash on his trunk.
• Physical examination revealed bilateral tibia periostitis on bone scintigraphy.
• Serologic tests confirmed active syphilis infection.

Findings:

• The patient was diagnosed with secondary syphilis.
• The clinical presentation included bilateral tibia periostitis, a rare but recognized manifestation of secondary syphilis.
• Positive serologic tests indicated an active infection requiring prompt treatment.

Implications:

• This case highlights the importance of considering syphilis in the differential diagnosis of unexplained periostitis, especially in the presence of dermatological findings.
• Prompt diagnosis and treatment of secondary syphilis are essential to prevent long-term complications.
• Rheumatologists and infectious disease specialists should be aware of the diverse clinical spectrum of syphilis.