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What is Syphilis?

Syphilis is a complex infectious disease caused by an unusual bacterium called a spirochete. The spirochete penetrates broken skin or mucous membranes in the genitalia, rectum, or mouth during intimate sexual contact with an infected individual. After gaining access, the organisms pass quickly through the bloodstream and lymphatic system. Within hours, the organism has spread to all parts of the body.

Untreated, the syphilis bacterium can move throughout the body, damaging many organs over time. The disease progresses through the following stages of infection: primary, secondary, tertiary, and late stages. Each of these stages displays characteristic symptoms and physical signs that are used to diagnose the infection. An infected individual can infect others during the first two stages, and during the early latent stage, which usually lasts one to two years. Although not contagious in its late stages, untreated syphilis can cause serious heart abnormalities, mental disorders, blindness, neurological problems, and death.

Syphilis is typically seen in individuals 15 to 35 years old. A sexually transmitted disease, there is approximately a 30% risk of contracting the disease during a single contact with an infected person. Although spread almost exclusively by sexual contact, it is possible for syphilis to be passed from mother to fetus during pregnancy (congenital). After many years of a decrease in the incidence of syphilis, it is again on the rise in many US cities.

How is it diagnosed?

Syphilis is diagnosed at each stage of infection by a combination of characteristic symptoms and detection of the infecting spirochetes. Between each stage is a variable period of time without symptoms or signs of the disease.

History: The first symptom of primary stage syphilis is a painless ulcer (chancre) with a hard, wet base. Although the usual site is the genitals, the chancre may also appear on the anus, rectum, cervix, mouth, or fingers. Because the chancre is ordinarily painless and sometimes occurs inside the body, it may go unnoticed. The chancre disappears within four to eight weeks whether or not treatment is obtained. If not treated during this primary stage, syphilis may progress through the other three stages.

The secondary stage of syphilis begins six to twelve weeks after infection. The most obvious feature is a skin rash that may cover the whole body, or may appear only in a few areas, such as the palms of the hands or soles of the feet. The rash may be temporary (transient), recurrent, or may last for months. On fair skin, the rash consists of crops of pinkish round spots. On darker skin, the rash is pigmented, appearing darker than the normal skin color. Other symptoms may include a low-grade fever, sore throat, headache, fatigue, loss of appetite, and generalized pain in joints and muscles. Hair may fall out in patches. Thickened gray or pink patches (condylomata lata) may develop in moist skin areas, such as the vulva or anus. Because active bacteria are present in these sores, any physical contact with the broken skin of an infected individual may spread the infection at this stage. Although symptoms will disappear without treatment, they may come and go over the next one to two years.

If untreated, syphilis then lapses into a latent or inactive stage. During this stage, which may last for a few years or for the rest of the individual's life, the disease is no longer contagious and no symptoms are present. About 30% of untreated cases go on to develop the complications of late stage (tertiary) syphilis.

The tertiary stage of syphilis usually starts within ten years of infection. In this final stage, the bacteria can damage the heart, the eyes (causing blindness), the bones or joints, and almost any other part of the body. Approximately five percent of individuals with untreated syphilis develop neurosyphilis, a chronic inflammation of the brain and its lining, characterized by a gradual deterioration of memory and alterations in personality and behavior. Other symptoms of neurosyphilis may include headache, stiff neck, fever, tremors, and weakness. Some individuals develop seizures. When the blood vessels are affected, symptoms of stroke can occur including numbness, weakness, or visual complaints. Tabes dorsalis, a complication that affects part of the spinal cord, can cause sharp pains, abnormalities of sensation, lack of coordination, and incontinence.

Physical exam during primary syphilis may reveal a single, hard, painless ulcer (chancre) on the genitals, mouth, anus, rectum, cervix, or fingers. However, in some cases the chancre may be painful or multiply. Lymph nodes may become painlessly enlarged and rubbery in the area surrounding the chancre. In secondary syphilis, a painless, non-itching rash, which usually begins on the palms of the hands or soles of the feet, may spread to involve the whole body. Lymph nodes may become swollen throughout the body. Meningitis (inflammation of the membranes of the spinal cord or brain) may occur during this stage. An enlarged spleen, liver inflammation (hepatitis), stomach ulceration, and eye infection are less common symptoms of secondary stage syphilis.

Symptoms are absent during the latent stage.

During the tertiary stage, gumma formation (localized areas of dead tissue often enclosed by scar tissue) may involve the bones, roof of the mouth (palate), tongue, nasal septum, skin, and other organs of the body. Gummas can be life threatening when located in the heart or coronary arteries. Cardiovascular syphilis can affect the aorta (main artery of the body), resulting in aneurysm formation and heart valve disease. Neurosyphilis can cause progressive brain damage and general paralysis (general paresis). Tabes dorsalis can cause abnormalities of sensation, incoordination, and incontinence.

Tests: Definitive diagnosis of primary syphilis is made by identifying spirochetes in samples of the chancre fluid as seen under a microscope. Diagnosis of secondary stage syphilis is confirmed with blood tests such as the Venereal Disease Research Laboratory (VDRL) or the fluorescent treponemal antibody absorption test for anti-spirochete antibodies, or by microscopic observation of the spirochetes from biopsies of the skin rash or lymph nodes. Although symptoms and physical signs are absent during the latent stage of syphilis, the disease may be progressing nonetheless. The spinal fluid should be monitored for the advance of central nervous system disease (neurosyphilis). Additionally, a chest x-ray can be used to observe the width of the aorta and monitor the progression of cardiovascular syphilis, which can progress even in the absence of positive laboratory blood tests.

The accuracy of antibody testing is undependable in the tertiary stage. Cerebrospinal fluid can be examined microscopically for the spirochete. A chest x-ray may reveal widening of the aorta next to the heart.

How is Syphilis treated?

Successful therapy involves the administration of high levels of antibiotics. Although early syphilis can often be treated with a single large injection, later forms of syphilis require a longer course of treatment. Individuals treated with antibiotics may suffer a severe reaction within six to twelve hours as a result of the body's response to the sudden death of large numbers of spirochetes. Because some individuals do not respond to the usual doses of antibiotics, it is important to have periodic blood tests to ensure that the infectious agent has been completely destroyed. Antibiotic treatment is most successful in the primary and secondary stages of disease, although tertiary skin and bone lesions also respond well. For other forms of tertiary syphilis, antibiotic treatment is not as effective.

Follow-up evaluations of the spinal fluid should be performed in all cases of neurosyphilis for up to two years following treatment. Hospitalization may be required for advanced dementia or cardiovascular disease associated with tertiary stage syphilis. Organ damage already caused by the disease cannot be reversed.


Minocin (Minocycline)

What might complicate it?

Approximately five percent of individuals with untreated syphilis develop chronic inflammation of the brain and its lining, resulting in brain damage and general paresis within ten to fifteen years after the primary infection. Another complication of neurosyphilis is tabes dorsalis, in which the spinal cord is affected. Cardiovascular syphilis affects the aorta, leading to aneurysm formation and heart valve disease. Infections of the upper respiratory tract, mouth or tongue may lead to functional disabilities from scarring or tissue necrosis. Gummas of the esophagus or digestive tract are often diagnosed mistakenly as ulcers or tumors and result in unnecessary chemotherapy or surgery. The same is true for gummas of the breast, liver, kidneys, and bladder.

Individuals with impaired immune systems normally have more extensive primary and secondary infections, and often progress more rapidly to tertiary stage syphilis. The absence of a normal immune response can interfere with the correct diagnosis of syphilis from blood and spinal fluid samples.

Simultaneous chemotherapy for other diseases may interfere with effective antibiotic treatment.

Predicted outcome

The prognosis for primary and secondary syphilis is good, given antibiotic treatment, follow-up testing, and the absence of complicating co-infections or chemotherapy. Even when tertiary symptoms develop, they might be stopped with effective antibiotic therapy. However, if the disease is allowed to progress to late stages without therapy, the prognosis is variable.

For cardiovascular syphilis, the prognosis is poor because most cases are diagnosed after significant cardiovascular damage has occurred. With treatment, the damage may be stopped or slowed but cannot be reversed. Increasing disability is anticipated.

In untreated nervous system syphilis (neurosyphilis), the disease is progressive and the ultimate outcome is fatal. The duration of life from the first mental symptoms to death can vary from a few months to five or six years. With antibiotic treatment, some of the symptoms will slow in progression, but the effectiveness of treatment is variable.


  • The chancres of syphilis can resemble genital herpes simplex, trauma with or without secondary bacterial infection, scabies, and less commonly, herpes zoster, carcinoma, chancroid, tuberculosis and amebic ulceration.
  • The generalized rash is similar to other infections including measles, rubella, drug rash, typhoid fever and leprosy.
  • More severe rashes may resemble acne vulgaris, scabies, psoriasis, seborrhea, fungal infections or even human papilloma virus-induced warts.
  • Enlarged lymph nodes resemble those of glandular fever from cytomegalovirus or mononucleosis, HIV infection, Hodgkin's disease or lymphoma.
  • Mucosal ulceration may resemble that of herpes simplex virus infection.
  • Symptomatic neurosyphilis can be confused with many similar neurological diseases or conditions.
  • Other causes for acute meningitis are Lyme disease, tuberculosis, leptospirosis and enterovirus infection.
  • Cerebrovascular syphilis can be confused with other causes of stroke syndromes such as hypertension, cerebral atherosclerosis or systemic lupus erythematosus.
  • Other syndromes that may be confused with non-typical neurosyphilitic dementia include brain tumor, blood clots, arteriosclerotic brain vessels, Alzheimer's disease, multiple sclerosis, senile dementia and chronic alcoholism.

Appropriate specialists

Infectious disease specialist (especially if other infections, such as HIV, are present), cardiologist (for cardiovascular syphilis), neurologist (for neurosyphilis), and internist.

Seek Medical Attention

  • You or a family member has symptoms of syphilis.
  • The following occur during or after treatment:
    • Fever.
    • Skin rash, sore throat or swelling in any joint, such as the ankle or knee.
  • You once had syphilis and have not had a medical checkup in the past year.
  • You have had sexual contact with someone who has syphilis.

Last updated 6 April 2018