Late syphilis refers to the manifestations of untreated syphilis infection that emerge years or even decades after the initial exposure to the bacterium Treponema pallidum. It encompasses several distinct conditions, including cardiovascular syphilis, neurosyphilis, and gummatous syphilis, as well as a prolonged silent phase known as late latent syphilis. Once considered a disease of the past, late syphilis is becoming more clinically relevant as syphilis rates climb across the United States and globally.
How Syphilis Progresses to a Late Stage
Syphilis moves through stages when left untreated. The primary stage produces a painless sore called a chancre. The secondary stage brings rashes and flu-like symptoms. Both of these resolve on their own, which is part of what makes the disease so deceptive. After the secondary stage clears, the infection enters a latent period where no visible symptoms appear but the bacterium remains in the body. If this latent phase extends beyond a year, it is classified as late latent syphilis. Without treatment during these earlier windows, the disease can eventually progress into its most destructive forms.
The reason T. pallidum can linger in the body for so long comes down to how effectively it hides from the immune system. The bacterium has very few proteins on its outer surface, which makes intact organisms nearly invisible to immune defenses. It also undergoes antigenic variation of a surface-exposed protein called TprK, allowing it to change its appearance and dodge immune recognition over time.1PubMed Central. Biological basis for syphilis Its reduced genome makes it deeply dependent on the host for survival, and its flagella are tucked inside the cell rather than exposed on the surface, further limiting what the immune system can target.2PubMed. Syphilis Pathogenesis: Host Interactions, Immune Evasion, and Persistence of Treponema pallidum This combination of stealth features is what allows the infection to persist for years without producing symptoms, quietly seeding the conditions for late-stage disease.
Cardiovascular Syphilis
Cardiovascular syphilis typically appears 15 to 30 years after the initial infection and centers on the aorta, the body’s largest artery. The bacterium causes inflammation of the tiny blood vessels that supply the aortic wall itself, a process called obliterative endarteritis of the vasa vasorum. This starves the aortic wall of blood, weakens it, and eventually leads to aneurysm formation. The classic triad of cardiovascular syphilis includes a thoracic aortic aneurysm, aortic valve regurgitation (where the valve leaks blood backward), and narrowing of the coronary ostia, the small openings where the coronary arteries branch off the aorta.3PubMed. Syphilitic Cardiac and Vascular Disease: A Comprehensive Review
All three components of this triad are dangerous. An aortic aneurysm can rupture with fatal consequences. Coronary ostial stenosis restricts blood flow to the heart muscle and can mimic coronary artery disease, sometimes leading to chest pain or heart attacks that puzzle cardiologists who are not thinking about syphilis as a cause. Aortic regurgitation gradually overworks the heart. Because cardiovascular syphilis develops so slowly and its symptoms overlap with more common heart conditions, it is often diagnosed late or missed entirely in settings where clinicians are not considering infectious causes.
Neurosyphilis and Its Many Faces
Neurosyphilis is the invasion of the central nervous system by T. pallidum. While it can technically occur at any stage of syphilis, its most severe and recognizable forms belong to late disease. It takes two major clinical patterns: general paresis and tabes dorsalis, though these can overlap or present with features of both.
General paresis affects the brain and is essentially a form of dementia caused by syphilis. It brings progressive cognitive decline, personality changes, and psychiatric symptoms. Mood disturbances are especially common, with agitation being a frequent early feature. The condition is often misdiagnosed as a primary psychiatric illness like bipolar disorder, schizophrenia, or major depression, sometimes for years before someone thinks to test for syphilis.4PubMed Central. Clinical and neuropsychological characteristics of general paresis misdiagnosed as primary psychiatric disease What makes this particularly unfortunate is that, unlike most forms of dementia, general paresis can be treated and sometimes reversed with adequate antibiotic therapy if caught early enough. Syphilis can also cause depression, mania, psychosis, delirium, and personality changes even before full-blown dementia develops.5PubMed Central. Neurosyphilis: a case report
Tabes dorsalis, the other major form of late neurosyphilis, affects the spinal cord rather than the brain. It damages the posterior columns, which carry sensory information about body position and vibration. The most frequent early symptoms include limb numbness and lightning pains, sharp shooting pains that spread rapidly through the legs, trunk, or back. As the disease progresses, patients develop sensory ataxia, meaning they lose the ability to coordinate movement because they cannot properly sense where their limbs are in space. Urinary or fecal incontinence eventually affects a large majority of patients. On examination, classic signs include a positive Romberg test (loss of balance when standing with eyes closed), diminished or absent deep tendon reflexes in the lower limbs, a wide-based unsteady gait, and Argyll Robertson pupils, which are small pupils that react to focusing on a near object but not to light.6Infection and Drug Resistance. Diagnosing Tabes Dorsalis in HIV-Negative Patients: Clinical Features, Neuroimaging, and Laboratory Insights in the Modern Antibiotic Era
Gummatous Syphilis
Gummas are the hallmark of what was historically called “tertiary syphilis” in the classic textbook sense. These are soft, tumor-like growths made of granulomatous tissue, the body’s chronic inflammatory response to the lingering infection. They can form nearly anywhere: skin, bone, liver, and other organs. On the skin, they appear as firm nodules or plaques that may ulcerate. Under the microscope, they show characteristic features including dense collections of plasma cells and the same kind of small-vessel inflammation seen in cardiovascular syphilis.7PubMed Central. Syphilitic Gumma: A Rare Form of Cutaneous Tertiary Syphilis
Gummas have become rare in the antibiotic era precisely because most syphilis is now treated before it reaches this stage. When they do occur, they respond well to penicillin therapy, often resolving completely. Their rarity, however, means that clinicians encountering one for the first time may not recognize it, adding another layer to the diagnostic challenge.
When the Eyes and Ears Are Involved
Ocular syphilis and otosyphilis deserve special attention because they can cause permanent damage if not treated quickly, and they do not fit neatly into the traditional staging framework. Syphilis can affect the eyes or ears at any stage of infection, including early stages, though involvement becomes more concerning in later disease when it overlaps with neurosyphilis.
Ocular syphilis most commonly manifests as uveitis, an inflammation of the middle layer of the eye. While uveitis itself does not typically cause permanent blindness, optic nerve involvement does. A study of over 8,000 syphilis cases found 213 patients with ocular disease and 50 with blindness, and the blindness was concentrated among those with optic nerve damage rather than isolated uveitis.8PubMed Central. The importance of proper and prompt treatment of ocular syphilis: a lesson from permanent vision loss in 52 eyes This underscores why any visual symptoms in a person with syphilis should be treated as an emergency.
Otosyphilis produces hearing loss, tinnitus (ringing in the ears), or vertigo. Cases where both the eyes and ears are affected simultaneously are uncommon but documented, as in one report of a young man who presented with uveitis and tinnitus together, with audiometric testing confirming bilateral sensorineural hearing loss.9PubMed Central. All Eyes and Ears: A Case of Neurosyphilis Presenting With Simultaneous Ocular and Otic Involvement Both ocular and otic syphilis are treated with the same aggressive intravenous antibiotic regimens used for neurosyphilis, because the concern is that the bacterium has penetrated the central nervous system.
Why Syphilis Is Called the Great Imitator
One of the biggest obstacles to diagnosing late syphilis is that it can look like almost anything else. Syphilis has long carried the nickname “the great imitator,” and the label holds especially true for its later manifestations. Skin lesions can resemble psoriasis, lichen planus, fungal infections, or even lymphoma. Gummas on the skin can be confused with Kaposi’s sarcoma, sarcoidosis, leprosy, or foreign body reactions. Mucosal involvement can look like oral hairy leukoplakia. Diffuse hair loss from syphilis can mimic alopecia areata.10PubMed Central. Syphilis Mimicking Other Dermatological Diseases: Reactive Arthritis and Mucha-Habermann Disease The psychiatric symptoms of general paresis get attributed to primary mental illness. Cardiovascular syphilis is confused with garden-variety heart disease.
This mimicry is a major reason syphilis testing should be part of the workup for unexplained neurological symptoms, psychiatric presentations in younger adults, unusual skin lesions, or atypical cardiovascular findings, particularly in populations with higher syphilis prevalence.
How Late Syphilis Is Diagnosed
No single blood test can confirm syphilis on its own. Diagnosis requires two types of antibodies to be detected: nontreponemal antibodies (measured by tests like the RPR or VDRL) and treponemal antibodies (measured by tests like the FTA-ABS or TP-PA).11PubMed Central. Diagnostic tests for syphilis: New tests and new algorithms Nontreponemal tests give a titer that rises with active disease and falls after treatment, making them useful for tracking the infection’s activity. Treponemal tests detect antibodies that persist for life regardless of treatment, so they confirm past exposure but cannot distinguish active from treated infection.
When neurosyphilis is suspected, a lumbar puncture to examine cerebrospinal fluid is the next step. However, not every patient with late syphilis needs one. Research has found that neurosyphilis is very unlikely in patients with late latent syphilis who have a negative blood VDRL test. In one study, not a single patient with neurosyphilis tested VDRL-negative in the blood, and the median blood VDRL titer was substantially higher in patients with neurosyphilis than in those without.12PubMed. Neurosyphilis is unlikely in patients with late latent syphilis and a negative blood VDRL-test A negative blood VDRL in an otherwise asymptomatic patient with late latent syphilis can reasonably spare them the discomfort and risk of a spinal tap.
Treatment of Late Syphilis
Penicillin remains the cornerstone of syphilis treatment at every stage, and late syphilis is no exception. For late latent syphilis and gummatous or cardiovascular syphilis, the standard approach is benzathine penicillin G given as intramuscular injections over three weeks, totaling 7.2 million units.13PubMed. Treatment of late syphilis with 2.4 million units benzathine penicillin G (BPG): tolerance of single versus divided doses For neurosyphilis, including ocular and otic syphilis, treatment is more intensive: intravenous aqueous crystalline penicillin G given every four hours for 10 to 14 days. The reason for the difference is that benzathine penicillin, while excellent at maintaining prolonged low blood levels of the drug, does not reliably cross into the cerebrospinal fluid at high enough concentrations to clear the infection from the central nervous system.
For patients allergic to penicillin, doxycycline is the most studied alternative. Recent data support its use regardless of syphilis stage, including in people living with HIV, though the evidence base is smaller than for penicillin and the data in late-stage disease are more limited.14Open Forum Infectious Diseases. P-717. Serologic response to doxycycline versus penicillin for treatment of early or late stage syphilis For neurosyphilis specifically, desensitization to penicillin in a hospital setting is often preferred over switching to an alternative drug, because the stakes of incomplete central nervous system treatment are high.
The Jarisch-Herxheimer Reaction
A complication that catches many patients off guard is the Jarisch-Herxheimer reaction, a temporary worsening of symptoms that occurs within hours of starting antibiotic treatment. It is thought to be caused by the immune system’s response to the sudden die-off of large numbers of bacteria. In most syphilis cases, this manifests as fever, chills, headache, and muscle aches that resolve within a day. In neurosyphilis, however, the reaction can be more dramatic, including altered consciousness, changes in pupil reactivity, and focal neurological signs.15PubMed Central. Jarisch-Herxheimer reaction in a patient with neurosyphilis
Management of the reaction is largely supportive. Physical cooling, anti-inflammatory medications, and monitoring for neuropsychiatric symptoms are the main strategies. In neurosyphilis patients, these neuropsychiatric symptoms of the reaction typically resolve within two to seven days of starting treatment.16PubMed Central. Jarisch-Herxheimer reaction as a complication of penicillin G and ceftriaxone treatment in neurosyphilis Corticosteroids have been suggested as a way to prevent or blunt the reaction, particularly when treating neurosyphilis in patients where a severe reaction could be dangerous. Examining the cerebrospinal fluid before treatment may help predict who is at higher risk.15PubMed Central. Jarisch-Herxheimer reaction in a patient with neurosyphilis
HIV and the Risk of Late Syphilis
HIV and syphilis frequently overlap, and their interaction complicates diagnosis, treatment, and monitoring. People living with HIV who acquire syphilis face a higher risk of developing neurosyphilis, particularly if their immune system is not well controlled. The major risk factors for asymptomatic neurosyphilis in people with HIV include a low CD4 T-cell count, a high RPR titer, and lack of HIV viral suppression.17PubMed. Risk of neurosyphilis in HIV-infected persons with syphilis lacking signs or symptoms of central nervous system infection This means that people with HIV who are on effective antiretroviral therapy and have a well-suppressed viral load and healthy CD4 counts are at lower risk, but the threshold for investigating neurosyphilis remains lower in this population than in people without HIV.
Interestingly, among people with HIV who are on antiretroviral therapy and have achieved good immune recovery, the relationship between syphilis and immune markers becomes less straightforward. One study found that the majority of patients who tested positive for T. pallidum antibodies had CD4 counts above 350 and suppressed viral loads, suggesting that in the context of effective HIV treatment, syphilis does not necessarily track with poor immune status.18PubMed Central. Prevalence of syphilis, neurosyphilis and associated factors in a cross-sectional analysis of HIV infected patients attending Bugando Medical Centre, Mwanza, Tanzania The practical takeaway is that syphilis screening should be routine for everyone living with HIV, regardless of how well their HIV is controlled.
What Happens After Treatment
Successfully treating late syphilis does not always mean the blood tests go back to normal. A significant proportion of treated patients enter what is called the “serofast state,” where their nontreponemal antibody titer (like the RPR) fails to drop by the expected amount. The CDC defines this as less than a fourfold decrease in titer after 12 to 24 months for late syphilis.19PubMed Central. Serofast state after syphilis treatment: implications and recommendations for clinical practice. Narrative review
In a large study of over 1,300 treated syphilis patients, about a third remained serofast one year after treatment, and the rate of achieving a full serological cure decreased as the stage of syphilis advanced. Patients with tertiary syphilis were the least likely to achieve serological cure, while those with primary syphilis fared best. Being female, being older, and having certain baseline titer levels were also associated with staying serofast.20PubMed Central. Factors associated with serological cure and the serofast state of HIV-negative patients with primary, secondary, latent, and tertiary syphilis The serofast state does not necessarily mean treatment failed or that the infection is still active. In many cases, it represents immunological memory rather than ongoing infection. But it does create uncertainty for patients and clinicians, because distinguishing a serofast state from true treatment failure sometimes requires clinical judgment, re-examination, and occasionally retreatment.
Late Congenital Syphilis
Late syphilis is not exclusively a disease of adults who acquired the infection sexually. Congenital syphilis, transmitted from mother to child during pregnancy, has its own late manifestations that appear in childhood or adolescence. These include characteristic physical stigmata such as notched incisors (Hutchinson’s teeth), interstitial keratitis (inflammation of the cornea), saddle-nose deformity from cartilage destruction, and saber shins from chronic bone inflammation. Cases have been documented where children present with classic stigmata of congenital syphilis at the age of 10 or later, long after the window for early neonatal detection has closed.21PubMed Central. An inscrutable entity: A case report of late congenital syphilis
With congenital syphilis rates climbing alongside the adult syphilis resurgence, the possibility of late congenital presentations is worth keeping in mind, especially for pediatric providers evaluating children with unexplained dental abnormalities, joint problems, or corneal disease.
A Resurgent Epidemic
The reason late syphilis matters more now than it did two decades ago is simple: syphilis is surging. In the United States, reported syphilis cases rose from roughly 114,000 in 2018 to over 203,000 in 2022, with primary and secondary syphilis reaching about 59,000 cases in 2022, an incidence rate of 17.7 per 100,000 people.22PubMed Central. Unraveling the resurgence of syphilis: a deep dive into the epidemic sweeping across the United States; a mini review The increase has been driven by multiple factors, including the intersection with HIV epidemics, casual sexual encounters facilitated by dating technology, and global travel patterns.23PubMed Central. Resurgence of syphilis, the great imitator
More early syphilis today means more late syphilis in the future for anyone who slips through the cracks. Screening during pregnancy, routine screening for at-risk populations, and prompt treatment of early infections are the best tools for preventing the kind of organ damage described in this article. But for the patients who do progress to late disease, the evidence is clear that treatment works, and the earlier within that late window it begins, the better the outcome.
The Pre-Antibiotic Legacy
Before penicillin became available in the 1940s, the treatment options for syphilis were grim. Mercury, applied topically or taken internally, was the standard treatment for centuries despite its toxicity and uncertain effectiveness. Paleopathological studies examining skeletons from as far back as the 15th century have found elevated mercury levels in the bones of individuals with signs of syphilis, providing physical evidence of these treatments. Arsenic compounds were also used. Both were eventually abandoned in the early 20th century as their harm became undeniable and newer treatments emerged.24PubMed Central. Diagnostic Methods Used in Detecting Syphilis in Paleopathological Research—A Literature Review The arrival of penicillin transformed syphilis from a disease that destroyed the brain, heart, and bones of its victims over decades into one that could be cured with a few injections. The challenge now is making sure those injections reach everyone who needs them.