ICD-10-CM 2027
ICD-10 code for actinomycosis
From the official ICD-10-CM alphabetic index entry “Actinomycosis, actinomycotic”. Page updated September 29, 2026.
About coding actinomycosis
The ICD-10-CM code for actinomycosis is A42.9 (Actinomycosis, unspecified). The official index lists 8 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on A42.9.
Within A42, choose A42.9 (unspecified) only when documentation doesn't support a more specific option: pulmonary actinomycosis (A42.0), abdominal actinomycosis (A42.1), Cervicofacial actinomycosis (A42.2), actinomycotic sepsis (A42.7) and other forms of actinomycosis (A42.8).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 867 (Other Infectious and Parasitic Diseases Diagnoses with MCC, relative weight 2.1859), DRG 868 (Other Infectious and Parasitic Diseases Diagnoses with CC, relative weight 1.0235), DRG 869 (Other Infectious and Parasitic Diseases Diagnoses without CC/MCC, relative weight 0.6787), DRG 974 (HIV with Major Related Condition with MCC, relative weight 3.0506), DRG 975 (HIV with Major Related Condition with CC, relative weight 1.3252) and DRG 976 (HIV with Major Related Condition without CC/MCC, relative weight 0.8124), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites) and MDC 25 (Human Immunodeficiency Virus Infections), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
More specific actinomycosis codes (official index)
- with pneumonia A42.0 — Pulmonary actinomycosis
- abdominal A42.1 — Abdominal actinomycosis
- cervicofacial A42.2 — Cervicofacial actinomycosis
- cutaneous A42.89 — Other forms of actinomycosis
- gastrointestinal A42.1 — Abdominal actinomycosis
- pulmonary A42.0 — Pulmonary actinomycosis
- sepsis A42.7 — Actinomycotic sepsis
- specified site NEC A42.89 — Other forms of actinomycosis
Common questions about actinomycosis ICD-10 codes
What is the ICD-10 code for actinomycosis?
- A42.9 — Actinomycosis, unspecified. More specific codes apply when the documentation supports them: A42.0, A42.1, A42.2, A42.89 and others below.
What is the ICD-10 code for abdominal actinomycosis?
- A42.1 — Abdominal actinomycosis.
What is the ICD-10 code for cervicofacial actinomycosis?
- A42.2 — Cervicofacial actinomycosis.
What is the ICD-10 code for cutaneous actinomycosis?
- A42.89 — Other forms of actinomycosis.
What is the ICD-10 code for gastrointestinal actinomycosis?
- A42.1 — Abdominal actinomycosis.
What is the ICD-10 code for pulmonary actinomycosis?
- A42.0 — Pulmonary actinomycosis.
What is the ICD-10 code for sepsis actinomycosis?
- A42.7 — Actinomycotic sepsis.
Is A42.9 billable?
- Yes. A42.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can A42.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict A42.9 as a principal diagnosis.
Is A42.9 a CC or MCC?
- A42.9 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.