Diagnostic Dilemma in a Case of Anti-PL-7 Antibody-Positive Interstitial Lung Disease: When Autoimmune Alveolar Proteinosis Masquerades as Anti-Synthetase Syndrome.

Pulmonary alveolar proteinosis (PAP) and anti-PL-7 antibody-positive interstitial lung disease (ILD) share early radiographic similarities, yet their treatments differ significantly. This article reports a rare case of dual anti-PL-7 and anti-GM-CSF autoantibody positivity, initially misdiagnosed as anti-synthetase syndrome due to interstitial infiltrates and concurrent Nocardia/Aspergillus infections. Empirical glucocorticoid therapy worsened symptoms. Definitive PAP diagnosis was confirmed via milky bronchoalveolar lavage fluid (BALF) and anti-GM-CSF autoantibody detection, alongside incidental pulmonary embolism. Multidisciplinary intervention (antimicrobials, thrombolysis, and whole-lung lavage) improved oxygenation. Clinicians must consider PAP as a differential diagnosis in patients with atypical presentations before commencing immunosuppressive therapy. Multidisciplinary collaboration is crucial for managing complex PAP cases.