Excessive Dynamic Airway Collapse After Entecavir Use in a Patient With Pegylated Interferon-Induced Undifferentiated Connective Tissue Disease and Entecavir Use to Prevent Hepatitis B Virus Reactivation Upon Giving Rituximab.

Pegylated interferon-alpha (PEG-IFN-α) is an antiviral medication used to treat chronic hepatitis C virus (HCV) and hepatitis B virus (HBV) infections. It may result in rare but severe side effects, such as undifferentiated connective tissue disease (UCTD) and excessive dynamic airway collapse (EDAC), which can occur as delayed complications of PEG-IFN-α-induced UCTD. In cases where these complications arise, entecavir, employed for treating HBV infection, may be considered.