ICD-10 Code A31.9 – Mycobacterial infection, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A31.9 – Mycobacterial infection, unspecified
What it is
A31.9 identifies a mycobacterial infection when the organism or specific disease type is not further specified. Use it for documented mycobacterial disease that does not fit a more precise code.
Clinical signs
Clinical features vary; refer to documentation. Patients may have signs of infection involving the lung, skin, lymph nodes, or other sites, but the record must support a mycobacterial infection.
When to use this code
Use A31.9 when the provider documents a mycobacterial infection but does not name the species or a more specific diagnosis. It also applies when the chart confirms mycobacterial disease and no further detail is available. Check documentation before assigning it if a more specific A31 code is stated.
Do not use for
Do not use this code for tuberculosis or for a specifically identified nontuberculous mycobacterial infection with a dedicated code. If the organism or site is documented more clearly, code that condition instead.
Coding tip
Query the provider when the record says “mycobacterial infection” but does not identify the organism or site.