• A spirochete 0.1µm X 5-15µm.
• Cannot be seen by Gram staining but can be observed using darkfield microscopy.
• Microaerophilic (def).

Habitat

• Humans are the only natural host.

Source

• Typically transmitted sexually by contact with infected lesions; may be transmitted congenitally.

Epidemiology

• There were 32,000 cases of syphilis reported in the U.S. during 2003.

Clinical Disease

• Primary syphilis. Primary syphilis appears as a chancre (def), a painless ulcer with a raised border at the site of spirochete inoculation. The chancre is highly infectious. Regional painless lymphadenopathy (def) appears typically develops 1-2 weeks after the chancre. The chancre is abundant in spirochetes that subsequently disseminate via the lymphatics and blood. The chancre heals spontaneously within 2 months.
• Secondary syphilis. Secondary syphilis appears as flu-like symptoms with fever, headache, sore throat, anorexia (def) , myalgias (def) , lymphadenopathy, and a highly infectious generalized mucocutaneous rash that may resolve over a period of weeks to months.
• Late syphilis. A small percentage of cases progress to tertiary syphilis characterized by a chronic inflammatory response that can destroy pretty much any organ or tissue. This can result in blindness, dementia (def), arteritis (def), and granulomatous lesions called gummas (def).
• Congenital syphilis. In utero infection can result in latent infections, multiorgan malformations, or fetal death. Typically the newborn is initially asymptomatic but subsequently develops rhinitis (def) and a widespread macropapular rash (def). Late bony destruction and cardiovascular syphilis are common if the child is not treated with antibiotics.

From Syphilis, by Peter Liu, MD, Staff Physician, Department of Emergency Medicine, Virginia Hospital Center Arlington; Brian Euerle, MD, Program Director, Assistant Professor, Department of Surgery, Division of Emergency Medicine, University of Maryland Medical School; and Pranatharthi Haran Chandrasekar, MD, Director of Infectious Disease Fellowship, Professor, Department of Internal Medicine, Harper Hospital, Wayne State University School of Medicine