Secondary pulmonary alveolar proteinosis mimicking progression of interstitial lung disease during treatment for adult-onset still's disease: An autopsy case report.
Takashi Yamane, Taisuke Fujita, Atsushi Onoe et al.
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Case in brief
A 68-year-old woman with adult-onset Still’s disease-associated interstitial lung disease developed worsening respiratory failure while receiving immunosuppressive therapy, despite apparent control of systemic inflammation. New diffuse ground-glass opacities and a marked rise in serum KL-6 were attributed to progressive interstitial lung disease; repeated bronchoscopies showed organizing pneumonia but no evidence of pulmonary alveolar proteinosis (PAP). Anti-GM-CSF antibodies were negative, and PAP was not diagnosed during life. Respiratory failure progressed despite escalating treatment, and she died. Autopsy demonstrated secondary PAP with PAS-positive intra-alveolar material and myelodysplastic syndrome.
What made this case unusual
Secondary PAP was obscured by pre-existing interstitial lung disease and repeated bronchoscopic findings of organizing pneumonia; negative anti-GM-CSF antibody testing also did not establish the diagnosis. Autopsy revealed both PAP and myelodysplastic syndrome.
Diagnostic / clinical pearl
In a patient with connective tissue disease-associated ILD, a marked, progressive KL-6 rise should prompt reconsideration of the diagnosis, even when bronchoscopy does not show PAP and anti-GM-CSF antibodies are negative.
Why it matters
Misattributing deterioration to ILD progression may lead to intensified immunosuppression; the report highlights the risk of overlooking secondary PAP in this setting.