Idiopathic non-specific interstitial pneumonitis

This code represents a chronic, progressive lung disease characterized by inflammation and fibrosis of the lung interstitium without an identifiable cause. It is a diagnosis of exclusion, meaning other known causes of interstitial lung disease have been ruled out. The condition leads to impaired gas exchange and can result in significant respiratory compromise.

Use this code when the physician's documentation specifically identifies "idiopathic non-specific interstitial pneumonitis" after a thorough workup has excluded secondary causes. This diagnosis is typically made by a pulmonologist based on clinical presentation, imaging (HRCT), and often surgical lung biopsy findings.

• Ensure the documentation explicitly states "idiopathic" to differentiate from non-specific interstitial pneumonia due to a known cause.
• Do not code this with J84.89, as that code covers non-specific interstitial pneumonia (NSIP) when the cause is either unknown (NOS) or identified.
• Look for supporting documentation of extensive diagnostic workup to rule out other interstitial lung diseases, such as connective tissue disease-associated ILD, drug-induced ILD, or hypersensitivity pneumonitis.