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

Abstract

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.

Keywords: anti‐GM‐CSF autoantibody; anti‐PL‐7 antibody; multidisciplinary intervention; pulmonary alveolar proteinosis; steroid.

FIGURE 1

Dynamic evolution of the patient's pulmonary imaging: (A) The initial chest CT scan shows diffuse interstitial changes in both lungs accompanied by patchy ground‐glass opacities, and mild enlargement of the mediastinal lymph nodes. (B) Two months later, the re‐examination shows a reduction in the solid nodules in both lungs, but an increase in interstitial exudation in the lower lobes. (C) After misdiagnosis of RP‐ILD and treatment with glucocorticoids plus voriconazole, a typical ‘road‐paving stone sign’ with small interlobular septal grid‐like thickening is observed. (D) After total lung lavage, the lesions show significant absorption. (E, F) After sequential GM‐CSF nebulisation treatment for 1 and 3 months, the exudation improves progressively. Diagnosis and treatment process of combined intracranial Nocardia infection. (G) The initial enhanced MRI scan shows a ring‐shaped enhanced abscess in the right parietal lobe (arrow). (H) After 2 months of treatment with sulphonamides combined with linezolid, the lesion is absorbed. Figure (I) shows PAS staining (+), suggesting glycoprotein deposition (arrow).