Clinically amyopathic dermatomyositis with interstitial lung disease double-positive for anti-MDA5 and anti-PL12 antibodies.

Anti-melanoma differentiation-associated gene 5 (MDA5) and anti-aminoacyl-tRNA synthetase (ARS) antibodies are two major myositis-specific autoantibodies with distinct clinical features. However, the clinical course remains unclear in patients with clinically amyopathic dermatomyositis (CADM)-interstitial lung disease (ILD) who have co-existing anti-MDA5 and anti-ARS antibodies. Here, we describe the case of a 32-year-old woman with CADM-ILD who had anti-MDA5 and anti-PL12 antibodies. Her serum ferritin level was within the normal range. However, chest computed tomography revealed bilateral lower-lobe consolidation and ground-glass opacities. Treatment with prednisolone and immunosuppressants was successful in improving the skin lesion and ILD, but relapse occurred on reducing the dose of prednisolone. These clinical features match those of anti-ARS antibody-positive dermatomyositis-ILD. Because these two conditions show significantly different clinical features and require different intensities of treatment, clinicians should carefully follow-up these patients throughout the course of the disease.

Multicentric Castleman disease with infiltration of eosinophils to the lung.

A 41-year-old man presented with multiple superficial lymph nodes (LNs) swollen with elevated levels of serum immunoglobulin (Ig)G4 and C-reactive protein. Histological findings of his left inguinal LN revealed lymphoplasmacytic infiltration with numerous IgG4-positive plasma cells; IgG4+/IgG+ plasma cell ratio >40%. Chest computed tomography (CT) showed poorly defined centrilobular nodules, interlobular septal thickening, consolidations, and mediastinal LNs swelling. Bronchoalveolar lavage fluid (BALF) showed elevated eosinophils. A surgical lung biopsy showed focal dense eosinophil infiltration, in addition to lymphoplasmacytic infiltration, but few IgG4+ plasma cells. The diagnosis of multicentric Castleman disease (MCD) was made because of serum interleukin-6elevation. Treatment with prednisolone and tocilizumab improved his symptoms and lung lesions. This case shows that overlapping clinical and pathological features of MCD and IgG4-related disease may present in a single patient, showing the difficulty in distinguishing between these two diseases.