Early Syphilis (ICD-11: 1A61): Complete Coding and Diagnostic Guide

1. Introduction

Early syphilis represents one of the most critical and clinically relevant stages of infection caused by the bacterium Treponema pallidum. This phase encompasses the primary and secondary stages of the disease, as well as early latent syphilis lasting less than two years from initial infection. The importance of proper recognition and coding of this condition transcends merely administrative aspects, directly impacting epidemiological surveillance, contact tracing, and the implementation of public health strategies.

In recent decades, there has been a concerning resurgence of syphilis in various global contexts, especially among vulnerable populations and higher-risk groups. Transmission occurs predominantly through sexual contact, although vertical transmission during pregnancy represents an additional significant concern. Early syphilis is particularly important because it represents the period of greatest infectivity of the disease, when lesions contain a large quantity of treponemes and the risk of transmission is maximum.

Correct coding using the ICD-11 code 1A61 is fundamental to ensure accurate epidemiological data, facilitate longitudinal patient follow-up, ensure appropriate mandatory reporting, and allow appropriate resource allocation for control programs. Healthcare professionals, clinical coders, and managers must have a thorough understanding of diagnostic criteria and classification nuances to ensure accurate medical records and effectively contribute to the control of this sexually transmitted infection of great clinical and epidemiological relevance.

2. Correct ICD-11 Code

Code: 1A61

Description: Early syphilis

Parent category: Syphilis (higher category without specific code)

Official definition: Disease caused by infection with gram-negative bacterium Treponema pallidum pallidum, including primary and secondary stages of syphilis and early latent syphilis lasting less than 2 years. This disease is characterized by a single chancre in the first stage and diffuse rash in the second. Transmission is commonly through sexual contact.

This code was developed within the ICD-11 framework to provide greater specificity in the classification of different phases of syphilis. The explicit inclusion of the two-year period as a temporal milestone to define the early phase reflects current scientific understanding of the natural history of the disease and periods of greatest risk of transmission and complications. Code 1A61 groups manifestations that share common epidemiological, microbiological, and clinical characteristics, facilitating both clinical practice and research and health surveillance.

The hierarchical structure of ICD-11 allows this code to be complemented with additional specifiers when necessary, providing flexibility to document specific clinical characteristics without losing the ability to aggregate data for epidemiological purposes. This approach represents a significant advance compared to previous versions of the international classification of diseases.

3. When to Use This Code

The code 1A61 should be applied in specific clinical situations that characterize syphilis in its early stage. Below, we present detailed practical scenarios:

Scenario 1: Primary Syphilis with Typical Chancre A patient presents with a single, painless ulcerated lesion with hardened borders in the genital region, approximately 1-2 centimeters in diameter. The lesion appeared about three weeks after risky sexual exposure. On physical examination, bilateral non-tender inguinal lymphadenopathy is observed. Serological tests show reactive VDRL with low titer and positive FTA-Abs. In this case, code 1A61 is appropriate, as it characterizes the primary stage of early syphilis with classic manifestations.

Scenario 2: Secondary Syphilis with Cutaneous Manifestations A patient reports a history of genital lesion that spontaneously disappeared two months ago. Currently presents with generalized maculopapular rash, including palms and soles, without pruritus. Accompanied by general malaise, low-grade fever, and generalized lymphadenopathy. Serological tests demonstrate VDRL with high titer and positive treponemal tests. This presentation represents secondary syphilis, appropriately coded as 1A61.

Scenario 3: Secondary Syphilis with Condyloma Latum An individual presents with verrucous, moist, and raised lesions in the perianal and genital region, associated with mucosal plaques in the oral cavity. Denies history of chancre but admits multiple unprotected sexual exposures in the last six months. Serology shows high reactivity on both non-treponemal and treponemal tests. These secondary manifestations of syphilis fully justify the use of code 1A61.

Scenario 4: Early Latent Syphilis Diagnosed by Screening During routine screening, an asymptomatic patient presents with positive serology for syphilis. Detailed investigation reveals that a test performed 18 months ago was negative. There are no current signs or symptoms, but documented seroconversion within two years characterizes early latent syphilis, appropriately coded as 1A61.

Scenario 5: Early Syphilis with Neurological Manifestations A patient with recently diagnosed secondary syphilis (three months ago) develops persistent headache, visual disturbances, and neck stiffness. Analysis of cerebrospinal fluid demonstrates lymphocytic pleocytosis and positive VDRL in CSF. Although there is neurological involvement, the time since initial infection (less than two years) still classifies the case as early syphilis, justifying code 1A61, which may be supplemented with additional codes for specific neurological manifestations.

Scenario 6: Documented Reinfection A patient previously treated for syphilis three years ago, with serology demonstrating adequate cure (non-reactive VDRL), presents with new genital chancre and significant elevation in VDRL titers, characterizing reinfection. This new infection, being in the early stage, should be coded as 1A61, regardless of the previous history of treatment.

4. When NOT to Use This Code

It is essential to recognize situations in which code 1A61 is not appropriate, avoiding classification errors that may compromise the quality of epidemiological data and appropriate clinical management.

Exclusion for Early Congenital Syphilis: When syphilitic infection is acquired through vertical transmission during pregnancy or delivery, manifesting in the first two years of the child's life, the appropriate code is not 1A61, but rather the specific code for early congenital syphilis. The differentiation is crucial because congenital syphilis presents distinct clinical manifestations, different prognosis, and specific epidemiological implications related to prenatal control.

Exclusion for Late Syphilis: When the infection has a duration exceeding two years or presents typical manifestations of late phase (such as syphilitic gummas, significant cardiovascular involvement, or late neurosyphilis), code 1A61 should not be used. The two-year time threshold is essential for differentiation between early and late syphilis, reflecting differences in infectivity, treatment response, and potential for complications.

Exclusion for Unspecified Latent Syphilis: In situations where it is not possible to determine with precision when the initial infection occurred and there is no way to establish whether the duration is less than or greater than two years, the appropriate code is that for unspecified latent syphilis, not 1A61. This situation is common when patients are diagnosed through screening without detailed clinical history available.

Differential Diagnoses That Should Not Be Coded as 1A61: Genital lesions caused by other etiologies, such as herpes simplex, chancroid, lymphogranuloma venereum, or donovanosis, should not be coded as early syphilis even when there is clinical similarity. Laboratory confirmation is essential before applying the code. Similarly, skin eruptions from other causes (such as pityriasis rosea, drug reactions, or other dermatoses) should not be classified as secondary syphilis without adequate serological confirmation.

5. Step-by-Step Coding Process

Step 1: Assess Diagnostic Criteria

The diagnosis of early syphilis requires a systematic approach combining clinical, epidemiological, and laboratory elements. Initially, a detailed history should be obtained investigating history of risky sexual exposure, presence or history of genital lesions, systemic symptoms, and mucocutaneous manifestations. Complete physical examination is fundamental, including careful inspection of genitalia, oral cavity, skin (especially palms and soles), lymph nodes, and basic neurological examination.

Laboratory confirmation involves serological tests in two categories: non-treponemal tests (such as VDRL or RPR) and treponemal tests (such as FTA-Abs, TPPA, or immunoenzyme tests). The combination of both types of tests is essential for definitive diagnosis. In primary lesions, dark-field microscopy or direct detection tests may be utilized when available. Documentation of time since exposure or since the appearance of first manifestations is crucial for properly classifying the disease phase.

Step 2: Verify Specifiers

After confirming the diagnosis of syphilis, it is necessary to determine specifically which phase the disease is in. To apply code 1A61, it must be verified that the infection has been present for less than two years. This can be established through: documented history of seroconversion, appearance of primary or secondary symptoms within the specified period, or documentation of previous negative test within the last two years.

It should be classified whether the patient presents with primary syphilis (presence of chancre), secondary (systemic and mucocutaneous manifestations), or early latent (absence of symptoms but positive serology with less than two years duration). This more specific classification, although using the same main code 1A61, may be documented in the clinical description for greater precision of the medical record. The severity of manifestations and presence of complications should be documented, as they may require complementary codes.

Step 3: Differentiate from Other Codes

Differentiation from 1A60 (Congenital Syphilis): The fundamental distinction is the route of transmission. Code 1A60 is used exclusively for infections acquired through vertical transmission (mother-to-child during pregnancy or delivery), typically manifesting in children. Code 1A61 is used for infections acquired, predominantly through sexual route, at any age. The clinical presentation also differs significantly, with congenital syphilis presenting specific manifestations such as hepatosplenomegaly, characteristic bone alterations, and late manifestations such as Hutchinson teeth.

Differentiation from 1A62 (Late Syphilis): The temporal criterion is the main differentiator. Infections lasting longer than two years or presenting typical late-phase manifestations (gummas, cardiovascular involvement such as aortitis or aneurysm, late neurosyphilis with tabes dorsalis or general paresis of the insane) should be coded as 1A62. Early syphilis (1A61) is characterized by greater infectivity, faster response to treatment, and typical primary and secondary manifestations.

Differentiation from 1A63 (Unspecified Latent Syphilis): When it is not possible to determine with precision the duration of infection and there are no clinical or documentary elements that allow establishing whether the infection has been present for less or more than two years, code 1A63 is used. This situation is common in patients diagnosed during routine screening without known previous history. If there is documentation of negative test within the last two years or clearly early manifestations, 1A61 should be used.

Step 4: Necessary Documentation

Adequate documentation is essential to justify coding and allow appropriate follow-up. The medical record should include:

Checklist of Mandatory Information:

Date and type of risky exposure (when known)
Detailed description of clinical manifestations present or previous
Complete serological test results (type of test, titer, date)
Estimated or documented time since initial infection
History of previous serological tests and their results
Presence or absence of systemic symptoms
Investigation of sexual partners and contact tracing
Evaluation of relevant comorbidities (especially HIV)
Therapeutic plan instituted

This documentation should be clear, objective, and allow other professionals to understand the diagnostic reasoning and justification for the chosen coding. The quality of documentation directly impacts continuity of care, clinical research, and epidemiological surveillance.

6. Complete Practical Example

Clinical Case:

A 28-year-old male patient seeks medical care reporting the appearance of "red spots" on his body for approximately two weeks. During the history of present illness, he reports that approximately two months ago he presented with a "sore" on the penis that disappeared spontaneously after three weeks, without having sought medical care at that time. He admits to having had multiple sexual partners in the last six months, with inconsistent condom use.

On physical examination, a generalized erythematous maculopapular rash is observed, non-pruritic, involving the trunk, upper and lower extremities, including the palms of the hands and soles of the feet. Bilateral cervical, axillary, and inguinal lymphadenopathy is identified, with mobile, elastic, and non-tender lymph nodes. There are no active genital lesions at the time of examination. The patient also reports general malaise, intermittent low-grade fever, and mild headache in recent weeks.

Laboratory tests were requested including VDRL, which returned reactive with a titer of 1:128, and FTA-Abs, which resulted positive. Rapid HIV test was performed, resulting negative. Complete blood count showed mild leukocytosis without other significant alterations. Liver and renal function within normal parameters.

Step-by-Step Coding:

Criteria Analysis: The patient presents with a clinical history compatible with prior primary syphilis (ulcerated genital lesion that disappeared spontaneously) followed by typical secondary manifestations (maculopapular rash involving palms and soles, generalized lymphadenopathy, systemic symptoms). Serological confirmation with high-titer VDRL and positive treponemal test definitively establishes the diagnosis of syphilis. The time since the appearance of the first manifestations (approximately two months) clearly places the infection in the early phase, specifically in the secondary stage.

Code Selected: 1A61 - Early Syphilis

Complete Justification: The code 1A61 is appropriate because: (1) there is definitive laboratory confirmation of syphilis through serological tests; (2) the duration of infection is clearly less than two years; (3) the clinical manifestations are typical of secondary syphilis, which is included in the definition of early syphilis; (4) this is not congenital syphilis (acquired infection, not vertical transmission); (5) there are no manifestations of late phase; (6) the time of infection can be estimated with reasonable precision.

Complementary Codes: Depending on the coding system used and recording needs, codes may be added to document specific manifestations, such as the code for generalized lymphadenopathy or for specific dermatological manifestations. The negative HIV result is also clinically relevant and should be documented, as HIV-syphilis coinfection has specific therapeutic and prognostic implications.

Additional Documentation: In the medical record, it should be documented that the patient was counseled about the nature of the infection, the need for treatment, the importance of notifying and screening sexual partners, and precautions to prevent transmission. The therapeutic plan with benzathine penicillin should be clearly described, including dose, route of administration, and regimen. Follow-up should be scheduled to monitor therapeutic response through quantitative serological tests at appropriate intervals (usually 3, 6, and 12 months).

7. Related Codes and Differentiation

Within the Same Category:

1A60: Congenital Syphilis

When to use 1A60 vs. 1A61: Code 1A60 should be used exclusively for cases of syphilis acquired through vertical transmission, from the infected mother to the fetus during pregnancy or to the newborn during delivery. Clinical presentation includes specific manifestations such as hepatosplenomegaly, jaundice, bullous skin lesions, characteristic radiological bone changes (periostitis, osteochondritis), bloody rhinitis, and Parrot's pseudoparalysis. In contrast, code 1A61 is used for acquired infections, typically through sexual contact, presenting with primary chancre and typical secondary manifestations in adolescents and adults.

Main difference: The route of transmission (vertical vs. sexual/direct contact) and the age group at presentation (neonatal/early childhood vs. adolescents/adults) are the fundamental differentiators. Congenital syphilis requires specific diagnostic and therapeutic approach, including maternal investigation and prolonged follow-up of the child.

1A62: Late Syphilis

When to use 1A62 vs. 1A61: Code 1A62 is appropriate when the infection has a duration greater than two years or when there are characteristic manifestations of the late phase. These include syphilitic gummas (destructive granulomatous lesions in skin, bones, or internal organs), cardiovascular complications (syphilitic aortitis, aortic insufficiency, aortic aneurysm), and late neurosyphilis (tabes dorsalis, general paresis of the insane, optic atrophy). Code 1A61 is used when the duration is less than two years and the manifestations are typical of the primary, secondary, or early latent phases.

Main difference: The temporal criterion (less than two years for 1A61, more than two years or late manifestations for 1A62) is the essential differentiator. Late syphilis generally presents with lower infectivity but greater potential for serious and irreversible complications. Treatment response may also differ, with late syphilis often requiring more prolonged therapeutic regimens.

1A63: Latent Syphilis Unspecified Whether Recent or Late

When to use 1A63 vs. 1A61: Code 1A63 should be applied in situations where there is serological confirmation of syphilis, the patient is asymptomatic (latent phase), but it is not possible to determine with precision the duration of infection. This situation is frequent in patients diagnosed during routine screening without prior testing history or inadequate documentation. If there is clear evidence that the infection is less than two years old (documented seroconversion, reliable history of recent primary or secondary manifestations), code 1A61 should be used.

Main difference: The availability of temporal information defines the choice. Code 1A61 requires documentation or reasonable evidence that the infection is less than two years old, while 1A63 is used when this information is not available. The accuracy of coding depends on the quality of the clinical history and documentation of previous serological tests.

Differential Diagnoses:

Various conditions can mimic manifestations of early syphilis and should be considered in the differential diagnosis. The primary chancre can be confused with genital ulcers caused by herpes simplex (usually multiple, painful, and recurrent), chancroid (painful ulcer with purulent base), lymphogranuloma venereum (transient ulcer followed by suppurative inguinal lymphadenopathy), or trauma. The rash of secondary syphilis can resemble pityriasis rosea (different distribution and morphology), drug eruption (history of medication use), viral exanthems, or other dermatoses. Serological confirmation is essential to definitively distinguish syphilis from these other conditions.

8. Differences with ICD-10

In the International Classification of Diseases in its tenth revision (ICD-10), early syphilis was coded using different codes depending on the specific stage: A51 for early syphilis, with subdivisions such as A51.0 (primary genital syphilis), A51.1 (primary anal syphilis), A51.2 (primary syphilis of other sites), A51.3 (secondary syphilis of skin and mucous membranes), A51.4 (other secondary syphilis), and A51.5 (early latent syphilis).

ICD-11, with code 1A61, simplifies this structure by grouping all manifestations of early syphilis under a single main code, allowing additional specifiers when necessary for greater detail. This change reflects a more pragmatic approach aligned with contemporary clinical practice, where the distinction between subtypes of early syphilis has fewer therapeutic and prognostic implications than the differentiation between early and late syphilis.

The practical impact of these changes includes simplification of the coding process, reduction of classification errors related to the choice among multiple subcodes, and facilitation of aggregated epidemiological analysis. For professionals familiar with ICD-10, it is important to recognize that all cases previously coded with codes from the A51 series should now be classified as 1A61 in ICD-11. This transition requires adequate training and updating of health information systems to ensure continuity and comparability of epidemiological data over time.

9. Frequently Asked Questions

How is the definitive diagnosis of early syphilis made?

The definitive diagnosis of early syphilis requires a combination of clinical, epidemiological, and laboratory elements. Clinically, the presence of a characteristic primary chancre (single, painless ulcer with hardened borders) or typical secondary manifestations (maculopapular rash including palms and soles, flat condylomas, mucosal plaques) in a patient with a history of risky sexual exposure strongly suggests the diagnosis. Laboratory confirmation is essential and is based on serological tests: non-treponemal tests (VDRL or RPR) that detect antibodies against cardiolipin and serve both for diagnosis and for monitoring treatment response, and treponemal tests (FTA-Abs, TPPA, immunoenzyme tests) that detect specific antibodies against Treponema pallidum and confirm infection. Positivity in both types of tests establishes the definitive diagnosis. In primary lesions, when available, dark-field microscopy or direct detection tests by PCR can demonstrate the presence of treponema, providing early diagnosis before complete seroconversion.

Is treatment available in public health systems?

Treatment for early syphilis is widely available in public health systems in most countries and is considered essential by the World Health Organization. Benzathine penicillin remains the treatment of choice, being highly effective, low-cost, and with a well-established safety profile. For primary, secondary, and early latent syphilis, the standard regimen consists of benzathine penicillin 2.4 million units intramuscularly in a single dose. Availability in public health services is generally good, although occasional temporary shortages may occur due to production or distribution issues. Patients allergic to penicillin can be treated with alternative antibiotics, such as doxycycline or azithromycin, although efficacy may be lower. Access to treatment is often integrated into sexually transmitted infection control programs, facilitating not only treatment of the index case but also screening and treatment of partners.

How long does treatment last and what follow-up is necessary?

For early syphilis, treatment with benzathine penicillin is administered in a single dose (for primary, secondary, and early latent syphilis), making the therapeutic regimen extremely convenient and favoring adherence. However, post-treatment follow-up is fundamental and should extend for at least 12 months. Monitoring of therapeutic response is performed through quantitative non-treponemal serological tests (VDRL or RPR) at regular intervals, typically at 3, 6, and 12 months after treatment. A progressive decline in titers is expected, with a reduction of at least fourfold (two dilution points) in 6 to 12 months indicating adequate response. Therapeutic failure is characterized by absence of decline in titers or sustained increase, which may indicate need for retreatment or investigation of neurosyphilis. Treponemal tests generally remain positive indefinitely (serological memory) and should not be used to monitor treatment response. Follow-up also includes guidance on prevention of reinfection, screening for other sexually transmitted infections, and evaluation of sexual partners.

Can this code be used in medical certificates and official documents?

The use of ICD codes in medical certificates and official documents must follow fundamental ethical principles of confidentiality and respect for patient privacy. In many contexts, legislation protects information related to sexually transmitted infections, recognizing the potential for stigmatization and discrimination. For work absence certificates or documents that will be presented to third parties, it is generally recommended to use generic terms such as "infectious disease under treatment" or simply indicate the need for absence without specifying the diagnosis. The specific ICD-11 code 1A61 should be reserved for internal medical documentation, hospital records, epidemiological surveillance systems, and situations where confidentiality can be assured. In documents that require diagnostic specification (such as medical reports for expert assessment or legal proceedings), the code may be included, but always with awareness of privacy implications and after appropriate discussion with the patient. Transparency with the patient about what will be documented and where this information will be used is fundamental to maintaining trust in the physician-patient relationship.

Should patients with HIV receive different coding or treatment?

Patients with HIV-syphilis coinfection represent a special clinical situation that requires particular attention, although the primary coding remains 1A61 for early syphilis. Coinfection is common due to shared transmission routes and similar risk behaviors. Clinically, HIV-positive patients may present with atypical manifestations of syphilis, faster progression between stages, greater risk of neurosyphilis, and altered serological response. Treatment remains based on benzathine penicillin, but many specialists recommend more intensive regimens, and evaluation for neurosyphilis (including lumbar puncture) should be considered more liberally. Serological follow-up should be more frequent and prolonged, as rates of therapeutic failure may be higher. In coding, in addition to code 1A61 for early syphilis, the appropriate code for HIV infection should be included, allowing identification of this special population for surveillance, research, and service planning purposes. Documentation of coinfection is essential to ensure appropriate clinical management and adequate follow-up.

Is it possible to have early syphilis more than once?

Yes, reinfection with syphilis is entirely possible and has become increasingly common in certain populations. Unlike some bacterial infections, syphilis does not confer lasting protective immunity after treatment. Cured individuals can become reinfected if exposed again to Treponema pallidum through sexual contact with an infected partner. The diagnosis of reinfection is established through: an increase of at least fourfold in non-treponemal test titers in a patient previously treated successfully, appearance of new primary or secondary lesions after documentation of cure, or seroconversion (non-treponemal tests that had become negative become positive again). Each episode of reinfection should be coded as 1A61 if in the early phase, regardless of history of previous infections. The occurrence of multiple reinfections signals the need for more intensive preventive interventions, counseling on risk reduction, more frequent screening, and evaluation of sexual partners. Proper documentation of previous episodes is important to distinguish reinfection from therapeutic failure.

What are the main complications if early syphilis is not treated?

Untreated early syphilis can progress to late syphilis, with serious and potentially fatal complications. Approximately one-third of untreated patients develop tertiary syphilis after years or decades of latency. Cardiovascular complications include syphilitic aortitis (inflammation of the aorta), aortic valve insufficiency, and thoracic aortic aneurysm, which can rupture with catastrophic consequences. Neurological complications of late neurosyphilis include tabes dorsalis (degeneration of the posterior columns of the spinal cord causing ataxia, lancinating pain, and sensory changes), general paresis of the insane (syphilitic dementia with progressive cognitive deterioration), optic atrophy leading to blindness, and cerebrovascular accidents. Syphilitic gummas are destructive granulomatous lesions that can affect skin, bones, liver, and other organs, causing significant deformities. Beyond the direct complications of the disease, untreated syphilis substantially increases the risk of HIV transmission, as ulcerated lesions facilitate viral entry. In pregnant women, untreated syphilis can result in congenital syphilis, with serious consequences for the fetus including fetal death, prematurity, and malformations. Early treatment of syphilis in the 1A61 phase essentially prevents all these complications, highlighting the importance of timely diagnosis and treatment.

How should screening and notification of sexual partners be conducted?

Screening of sexual partners is an essential component of syphilis control and should be initiated immediately after diagnosis. For primary syphilis, all sexual partners from the previous 3 months should be notified, tested, and presumptively treated. For secondary syphilis, the screening period extends to 6 months before symptom onset. For early latent syphilis, all partners from the previous 12 months should be investigated. Notification can be performed by the patient themselves (patient notification), by health professionals while maintaining confidentiality of the index case (provider notification), or through specialized third-party notification systems when available. The approach should be sensitive, non-punitive, and focused on public health. Notified partners should be tested serologically, but presumptive treatment (before test results) is often recommended for recently exposed partners, given the high probability of infection and the consequences of delayed treatment. Documentation of partner screening should be part of the medical record and is considered a quality indicator in the management of sexually transmitted infections. Barriers to effective screening include stigma, fear of violence or relationship breakdown, and difficulties in locating partners, especially in cases of casual or anonymous partnerships.

Keywords: ICD-11, code 1A61, early syphilis, Treponema pallidum, syphilitic chancre, primary syphilis, secondary syphilis, early latent syphilis, medical coding, syphilis diagnosis, penicillin treatment, sexually transmitted infections, epidemiological surveillance, serological tests, VDRL, FTA-Abs, cutaneous manifestations, partner screening, STI prevention.

External References

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References verified on 2026-02-04

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