A42.0

HCC Category Mapping

What This Code Means

Pulmonary actinomycosis is a chronic bacterial infection of the lungs caused by Actinomyces bacteria, which are normally found in the mouth and can cause slow-growing infections with abscess formation. This condition typically develops after aspiration or trauma and presents with persistent cough, fever, and chest symptoms.

Coding Tips

• •Actinomycosis is often misdiagnosed as tuberculosis or malignancy; verify the diagnosis is confirmed by culture or histopathology before coding
• •This code is specific to pulmonary involvement; if the infection affects other sites (cervicofacial, abdominal, CNS), use the appropriate A42 subcode instead

Clinical Significance

Pulmonary actinomycosis is a chronic bacterial lung infection caused by Actinomyces species (typically A. israelii), an anaerobic filamentous bacterium. It characteristically crosses tissue planes and can form draining sinus tracts. Often mimics lung cancer or tuberculosis on imaging, leading to diagnostic delay. Requires prolonged antibiotic therapy (6-12 months of penicillin or amoxicillin).

Documentation Requirements

• ✓Culture or histopathologic identification of Actinomyces species from pulmonary specimen
• ✓Characteristic sulfur granules on pathology if biopsy performed
• ✓Chest imaging showing consolidation, mass lesion, or cavitary disease (often mimics malignancy)
• ✓Clinical presentation (chronic cough, weight loss, hemoptysis, chest wall sinus tract)
• ✓Extended antibiotic treatment plan documented (typically 6-12 months)

Commonly Confused Codes