ICD-10 Code A18.81 – Tuberculosis of thyroid gland (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A18.81 – Tuberculosis of thyroid gland
What it is
A18.81 identifies tuberculosis infection involving the thyroid gland. Use it when documentation states that Mycobacterium tuberculosis affects the thyroid, usually as part of extrapulmonary TB.
Clinical signs
Clinical features vary; refer to documentation. Reported findings may include a thyroid mass, neck swelling, pain, or evidence of granulomatous infection on pathology or imaging.
When to use this code
Use this code when the provider documents thyroid tuberculosis, tuberculous thyroiditis, or TB confirmed in thyroid tissue. It may also apply when pathology or microbiology supports thyroid involvement by tuberculosis. Check documentation if the site of infection is unclear.
Do not use for
Do not use A18.81 for ordinary thyroiditis, thyroid nodules, or suspected TB without thyroid involvement. If the record only says disseminated or miliary tuberculosis, code the documented condition instead.
Coding tip
Confirm that the thyroid is explicitly named as the infected site before assigning A18.81.