ICD-10 code A57: Chancroid diagnosis and billing guide

Key Takeaways

ICD-10 Code A57 is the billable, specific diagnosis code for chancroid, an acute sexually transmitted genital ulcer disease caused by Haemophilus ducreyi.

A57 falls under ICD-10-CM category A50-A64 (infections with a predominantly sexual mode of transmission) and is valid for FY 2026 coding.

Synonyms include ulcus molle, anogenital ulcer (chancroid), and extragenital ulcer (chancroid). The ICD-9-CM crosswalk equivalent is 099.0.

Accurate documentation of confirmed or presumptive chancroid diagnosis supports clean claim submission. Pabau’s claims management software helps reduce STI coding errors.

Coders working in sexual health, primary care, and infectious disease settings encounter ICD-10 code A57 less often than common STI codes, which makes accurate assignment harder when it does appear. Misidentifying a genital ulcer disease, or selecting a non-specific code when A57 is appropriate, can trigger claim denials and documentation queries from payers.

This reference covers the definition of A57, its billability status, applicable synonyms, clinical background, related codes in the A50-A64 range, the ICD-9-CM crosswalk, and documentation requirements for practices managing sexual health clinic software workflows.

ICD-10 code A57: Definition and clinical description

ICD-10 code A57 designates chancroid, an acute, localized, sexually transmitted infection characterized by painful genital ulcers and inguinal lymphadenopathy. The causative organism is Haemophilus ducreyi, a gram-negative facultative anaerobic coccobacillus. According to the WHO ICD-10 classification browser, chancroid is classified within Chapter I (Certain infectious and parasitic diseases) under the block A50-A64, which covers infections with a predominantly sexual mode of transmission.

The condition is acute and autoinoculable, meaning the pathogen can spread from an initial ulcer site to other skin or mucosal surfaces through direct contact. Transmission is almost exclusively sexual, and outbreaks occur endemically in parts of sub-Saharan Africa, Southeast Asia, and some regions of Latin America. In the United States, reported cases are rare but do occur, and the condition remains reportable in many jurisdictions.

Billability status

A57 is a valid, billable, and specific ICD-10-CM diagnosis code for FY 2026. It is a single-axis code with no further subdivisions, meaning A57 itself is the most granular code available for chancroid. No additional character extension is required or available.

• Code type: Billable/specific ICD-10-CM diagnosis code
• Effective date: October 1, 2015 (ICD-10-CM adoption); valid through FY 2026
• Parent category: A50-A64 (infections with a predominantly sexual mode of transmission)
• ICD-10 chapter: A00-B99 (certain infectious and parasitic diseases)
• No subcodes: A57 is the terminal code; no fourth or fifth character extensions exist

Applicable synonyms and “Applicable To” notes for A57

The CMS ICD-10-CM tabular list includes an “Applicable To” note under ICD-10 code A57 listing ulcus molle as an accepted synonym. Additional synonyms documented in coding references include chancroid variants by anatomical site and clinical presentation. Understanding these synonyms matters because clinicians may document the diagnosis using different terminology, and coders must map those terms back to A57 correctly.

Coders should note that “soft chancre” is a colloquial equivalent sometimes recorded in clinical notes. It still maps to A57, but always verify documentation clarity before assigning. When charting is ambiguous between chancroid and syphilitic chancre, query the provider before coding.

ICD-9-CM crosswalk for ICD-10 code A57

For practices transitioning legacy records or reconciling historical claims, ICD-10 code A57 maps to ICD-9-CM Code 099.0 (Chancroid) via the CMS General Equivalence Mappings (GEMs). This is a one-to-one forward and backward mapping with no added complexity. The CMS ICD-10 codes page hosts the annual GEMs files for download, which coders can use to verify crosswalk accuracy for any fiscal year.

When pulling historic encounter data or auditing claims filed before October 2015, 099.0 is the equivalent code. Note that GEMs crosswalks are guidance documents, not authoritative claim reprocessing tools. Payers may apply their own crosswalk rules; verify with the relevant payer when reprocessing older claims. For accurate infectious disease coding, practitioners can reference the NCHS official ICD-10-CM guidelines published annually by CMS.

Related ICD-10 codes in the A50-A64 range

ICD-10 code A57 sits within the A50-A64 block, which covers a range of infections transmitted predominantly through sexual contact. Coders working in sexual health or infectious disease settings need to differentiate chancroid from clinically similar conditions, each of which has its own distinct code. ICD-10-CM coding guidelines emphasize code specificity, so selecting the most accurate code requires knowing how these conditions differ clinically.

The clinical distinction between chancroid (A57) and syphilitic chancre (A51.0 for primary genital syphilis) is particularly important. Both present as genital ulcers, but syphilitic ulcers are classically painless and indurated, while chancroid ulcers are painful and soft. Laboratory confirmation distinguishes them definitively. Use coding specificity as the guiding principle: do not assign A57 when documentation supports a different organism.

Streamline STI coding and documentation in your clinic

Pabau helps sexual health and primary care clinics manage patient records, digital intake forms, and claim submissions in one place, so coding workflows stay accurate and auditable.

Book a demo

Documentation requirements for ICD-10 code A57

Accurate assignment of ICD-10 code A57 depends on clinical documentation that supports either a confirmed or a clinically presumptive diagnosis of chancroid. The CDC/NCHS ICD-10-CM coding tool and the annual Official Guidelines for Coding and Reporting both require that coded diagnoses reflect the provider’s clinical judgment as documented in the medical record.

What documentation supports A57 assignment?

• Confirmed diagnosis: Laboratory isolation of H. ducreyi from ulcer exudate culture is the gold standard. Culture sensitivity is low (approximately 50–80% depending on laboratory conditions), so a negative culture does not rule out chancroid.
• Clinically probable diagnosis: Per CDC STI treatment guidelines, a probable chancroid diagnosis is supported by: (1) one or more painful genital ulcers; (2) no evidence of syphilis by dark-field examination or serology; (3) no evidence of herpes simplex virus (HSV) on culture or PCR; (4) clinical presentation consistent with chancroid.
• Provider documentation: The provider’s written diagnosis of “chancroid” or “ulcus molle” in the encounter note, progress note, or discharge summary supports A57 assignment even without lab confirmation, provided the clinical criteria are met.
• Notifiable disease context: In jurisdictions where chancroid is a reportable disease, the encounter record should document the diagnosis clearly to support public health reporting. Requirements vary by state or country; coders should not assume universal reportability.

Maintain HIPAA-compliant documentation practices when recording STI diagnoses. Patient records containing chancroid diagnoses are sensitive health information and must be protected accordingly. Using patient records management tools that support structured clinical notes reduces ambiguity and supports clean claim submission.

Coding guidelines and common errors for A57

The AAPC Codify ICD-10-CM lookup lists A57 with no special coding notes, Excludes 1 or Excludes 2 annotations, or “Use additional code” instructions at the code level. However, coders should apply the following general guidelines when working with ICD-10 code A57.

Principal vs. secondary diagnosis

When a patient is admitted or seen specifically for chancroid, A57 is the principal diagnosis. If chancroid is identified as a secondary condition during an encounter for another primary reason (for example, an HIV-positive patient presenting for antiretroviral management who is also found to have a concurrent chancroid infection), A57 is assigned as an additional code.

HIV comorbidity coding

When a patient has a documented HIV infection and presents with chancroid, ICD-10-CM Official Guidelines generally direct coders to assign B20 (HIV disease) as the principal diagnosis in inpatient settings when chancroid is considered an HIV-related condition, with A57 as an additional code. Verify sequencing against the current Official Guidelines for the specific clinical scenario. In outpatient settings, sequence the code that best reflects the reason for the visit. Always check the current Official Guidelines for Coding and Reporting, available via the ICD List reference tool, for annual updates to sequencing rules.

Common coding errors with A57

• Using A64 when A57 is supported: A64 (unspecified STD) should only be used when no specific STI code is documented. If chancroid is documented, A57 is required.
• Confusing A57 with A51.0 (primary genital syphilis): Both present as genital ulcers. Without clear provider documentation specifying the organism, query before coding.
• Assigning A57 on symptom-only documentation: Genital ulcer pain or inguinal lymphadenopathy alone does not support A57. The diagnosis must be documented.
• Failing to code concurrent STIs: Patients with chancroid have elevated risk for concurrent syphilis and HIV. Each confirmed concurrent diagnosis should be coded separately.

Practices handling STI coding workflows benefit from claims management software that flags incomplete diagnosis documentation before submission. A structured pre-claim review process catches the most common A57 coding errors at the point of encounter, not after a denial. Using digital intake forms that prompt providers to document organism-specific diagnoses also reduces reliance on provider query after the encounter.

Public health and notifiable disease context for A57

Chancroid is a nationally notifiable condition in the United States, per CDC surveillance requirements. However, notifiability rules operate at the state level, and specific reporting timelines and mechanisms vary by jurisdiction. Coding ICD-10 code A57 does not automatically trigger a public health report, but accurate diagnosis coding is a prerequisite for population-level disease surveillance.

Clinics operating under sexual health mandates should confirm their state’s reporting obligations for chancroid. Using compliance management tools that track reportable disease documentation helps ensure the clinical record supports both billing and public health requirements. Maintaining a clear audit trail from diagnosis to report is particularly important in settings subject to HIPAA compliance for clinic software.

From a dermatology standpoint, chancroid may present in patients seen at dermatology EMR software-supported practices, particularly when the ulcer presentation is atypical or when the patient presents via dermatology rather than a sexual health service. In those settings, the same documentation and coding rules apply.

Conclusion

ICD-10 code A57 is a specific, billable code for chancroid that demands accurate clinical documentation before assignment. The most common errors involve defaulting to A64 when specificity is available, confusing A57 with syphilitic primary codes, or assigning A57 without documented provider diagnosis. Applying the correct code the first time reduces denials and supports both billing integrity and disease surveillance.

Pabau’s claims management software supports structured diagnosis documentation and pre-claim review workflows for sexual health and primary care clinics. To see how Pabau handles STI coding workflows end to end, book a demo.

Continue your research

Need a clinical software platform built for sexual health clinics? Sexual health clinic software covers the full patient journey from intake to discharge documentation.

Looking for tools to reduce diagnostic coding errors? Claims management software from Pabau helps flag incomplete diagnosis records before submission.

Want a compliance-ready system for HIPAA-sensitive STI records? HIPAA compliance for medical offices outlines the documentation controls your practice needs.

Frequently Asked Questions