Derm Dx: A single chancre progresses to a diffuse rash

Syphilis is a sexually transmitted disease caused by the spirochete Treponema pallidum, that can be transmitted from contact with an infected lesion or congenitally from mother to child. Because syphilis has multiple presentations, it is known as the "great imitator,"...

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Syphilis is a sexually transmitted disease caused by the spirochete Treponema pallidum, that can be transmitted from contact with an infected lesion or congenitally from mother to child.

Because syphilis has multiple presentations, it is known as the “great imitator,” and is often mistaken for other conditions. A highly infectious, painless chancre with a punched out base and rolled out edges develops at the site of transmission about three to six weeks after transmission. This initial lesion resolves in four to six weeks.

In the second phase of syphilis, weeks four to 10, the spirochetes are multiplying and spreading throughout the body. A rash consisting of macular lesions, sometimes popular or pustule, spreads over the body and may involve the palms, soles, and oral mucosae. The rash can be accompanied by malaise, fever, myalgias, arthralgias and lymphadenopathy and is infectious. Other skin findings of secondary syphilis are condylomata latum and patchy alopecia.

After secondary syphilis, patients may enter a latent phase of disease in which symptoms resolve, but remains seroreactive. Some patient experience recurrences of secondary rashes. If left untreated, about one third of patients with secondary syphilis will go on to develop a tertiary form of the disease.

Tertiary syphilis develops over months to years and involves slow inflammatory damage to tissues including nerves and blood vessels. The 3 general categories of tertiary syphilis are gummatous syphilis (also called late benign), cardiovascular syphilis, and neurosyphilis.

Gummatous syphilis is characterized by granulomatous lesions, called gummas, which are mainly found in the skin, bones, and liver, but may affect any organ. They may break down and form ulcers, eventually becoming fibrotic. These lesions are noninfectious.

Cardiovascular syphilis occurs at least 10 years after primary infection. The most common manifestation is aneurysm formation in the ascending aorta, caused by chronic inflammatory destruction of the vasa vasorum, the penetrating vessels that nourish the walls of large arteries. Aortic valve insufficiency may result.

Neurosyphilis has several forms. If the spirochete invades the central nervous system (CNS), syphilitic meningitis results. Syphilitic meningitis is an early manifestation, usually occurring within 6 months of the primary infection. Cerebrospinal fluid (CSF) shows high protein, low glucose, high lymphocyte count, and positive syphilis serology.

Meningovascular syphilis occurs as a result of damage to the blood vessels of the meninges, brain, and spinal cord, leading to infarctions causing a wide spectrum of neurologic impairments. Tabes dorsalis develops as the posterior columns and dorsal roots of the spinal cord are damaged. Posterior column impairment results in impaired vibration and proprioceptive sensation, leading to a wide-based gait.

Disruption of the dorsal roots leads to loss of pain and temperature sensation and areflexia. Damage to the cortical regions of the brain leads to general paresis, formerly called “general paresis of the insane,” which mimics other forms of dementia. Impairment of memory and speech, personality changes, irritability, and psychotic symptoms develop and may advance to progressive dementia. The Argyll-Robertson pupil, a pupil that does not react to light but does constrict during accommodation, may be seen in tabes dorsalis and general paresis. The precise location of the lesion causing this phenomenon is unknown.

Congenital syphilis, discussed briefly here, is a veritable potpourri of antiquated medical terminology. The treponemes readily cross the placental barrier and infect the fetus, causing a high rate of spontaneous abortion and stillbirth. Within the first 2 years of life, symptoms are similar to severe adult secondary syphilis with widespread condylomata latum and rash. “Snuffles” describes the mucopurulent rhinitis caused by involvement of the nasal mucosae.

Later manifestations of congenital syphilis include bone and teeth deformities including “saddle nose” due to destruction of the nasal septum, “saber shins” due to inflammation and bowing of the tibia, “Clutton’s joints” due to inflammation of the knee joints, “Hutchinson’s teeth” in which the upper incisors are widely spaced and notched, and “mulberry molars” in which the molars have too many cusps.

Diagnosis

Serologic testing is considered the standard method of detection for all stages of syphilis after an initial physical exam, performed with gloves to prevent infection from contagious lesions. Nontreponemal tests, including the Venereal Disease Research Laboratory test, and the Rapid Plasma Reagin test, can be used as an initial screening test (78-86% sensitivity for primary syphilis, 100% sensitivity for secondary and 95%-98% for tertiary; specificity ranges from 85%-99%).  Nontreponemal tests usually become nonreactive with time after treatment. However, in some patients, nontreponemal antibodies can persist, sometimes for the life of the patient.

Because of the possibility of false-positive results, confirmation for any positive nontreponemal test should follow with a fluorescent treponemal antibody absorption test (84% specificity for primary syphilis; 96% specifity and 100% sensitivity for all other stages). 

Patients with confirmed syphilis infections should be tested for other sexually transmitted diseases, including HIV.

Treatment

Penicillin has been established as an effective treatment. Commonly prescribed antibiotics include penicillin G benzathene, as well as azithromycin, doxycycline. Clinicians can access more detailed treatment guidelines for each stage of the disease at the CDC’s website.

The prognosis in treated primary and secondary syphilis is excellent. T pallidum remains highly responsive to the penicillins and cure is likely.