Syphilis
Syphilis is an infection caused by the gram-negative spirochete (meaning spiral-shaped) bacteria called Treponema pallidum. It is mostly transmitted sexually, but vertical transmission (meaning from mother to child during pregnancy) and blood transfusion are also possible routes of transmission. In terms of pathophysiology, the spirochete invades the body and disseminates through lymphatics. It binds to endothelial cells, causing an inflammatory reaction, leading to endarteritis and perivascular inflammation.
Syphilis can be divided into many important stages. Let's first list the stages and their time intervals. The incubation period lasts for approximately 3 weeks, the primary stage lasts for 3-6 weeks, the secondary stage for 2-6 weeks (and is the most infectious stage), followed by a latent stage (with no defined time), and finally, the tertiary stage. Now, let’s discuss the high-yield features of each stage.
Syphilis is a localized disease in the primary stage. It initially involves the development of a chancre. This is a solitary papule usually on the genital region that progresses to a painless firm ulcer with hard borders. The secondary stage involves systemic spirochete spread, inducing an immunological reaction. As such, generalized lymphadenopathy occurs. It is at this stage where syphilis binds to endothelial cells. The binding of syphilis to endothelial cells in the skin and small capillaries develops a polymorphic maculopapular rash on extremities, trunk, palms, and soles. Condylomata lata is another key feature which involves wart-like papular erosions in the anogenital region, oral mucosa, and skin folds.
After the latent period, which does not have any clinical symptoms, tertiary syphilis can arise. Gumma is the first important symptom of tertiary syphilis. Gumma involves the formation of chronic destructive granulomas with a necrotic center that ulcerate. They can affect any organ, including the skin, internal organs, and bones. Vasa vasorum vasculitis (meaning vasculitis involving vessels supplying other blood vessels) can cause cardiovascular syphilis, leading to aortitis, aortic aneurysm, and aortic root dilation. Neurosyphilis is an important complication of tertiary syphilis. It involves the invasion of the CNS causing meningeal and cerebral inflammation. Some clinical features of this can be remembered through the mnemonic, “neurosyphilis makes me PANT”. This stands for personality change, Argyll Robertson pupil; where pupils show bilateral miosis and accommodate but do not react to light, neurological symptoms (dysarthria, hypotonia, tremors), and tabes dorsalis. Tabes dorsalis involves syphilis demyelinating the dorsal columns and DRG causing impaired proprioception (broad-based ataxia - Romberg test positive), absent dorsal tendon reflexes, and shooting pain and loss of sensation in the lower extremities.
To diagnose syphilis, nontreponemal serological tests such as the rapid plasma regain or RPR and venereal disease research laboratory test or VDRL are used to screen. These tests detect anticardiolipin antibodies called regain in the blood – however, these are not specific to syphilis. As such, treponemal tests such as the fluorescent treponemal antibody absorption test - FTA-ABS and PCR confirm the diagnosis.
In terms of treatment, a single IM dose of Benzathine penicillin G is used. In neurosyphilis, penicillin G is given intravenously for 10-14 days. It is important to treat all sexual contacts.