Case of Anti-Small Ubiquitin-Like Modifier Activating Enzyme Antibody-Positive Dermatomyositis with Sarcoidosis

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An autoantibody directed against small ubiquitin-like modifier activating enzyme (SAE) was identified in dermatomyositis (DM) patients with extensive rash and dysphagia in 2007¹. The incidence of anti-SAE antibodies is 1.5% to 3% in Asian patients with DM².

An 85-year-old woman who was diagnosed with sarcoidosis 11 years previously due to bilateral hilar-mediastinal lymphadenopathy (BHL) without other symptoms was referred to our department. She presented with periungual telangiectasia and erythema on her face, neck, shoulders, and upper extremities except in the scapular regions (Fig. 1). Histopathological findings of a skin biopsy obtained from her upper arm showed vacuolar changes in the basal layer and naked granulomas in contact with it (Fig. 2). Computed tomography (CT) revealed BHL without interstitial lung disease. Laboratory examinations revealed a positive titer (1:160) for antinuclear antibodies. Serum lactate dehydrogenase (LDH) and soluble interleukin (sIL)-2 receptor levels were slightly elevated at 259 mg/dl and 1,180 U/L, respectively. Creatinine phosphokinase (CK), aldolase and angiotensin converting enzyme levels were normal.

Fig. 1. Clinical findings: extensive rash on her neck, shoulder, and upper extremities. We received the patient’s consent form about publishing all photographic materials.

Fig. 2. H&E stain of the biopsy from her upper arm: vacuolar change in the basal layer and naked granulomas (original magnification ×100).

A diagnosis of sarcoidosis was established based on BHL, blood sampling, and histological findings. Prednisolone therapy was initiated, and the skin rash improved.

Five months after onset, the rash worsened, resulting in diffuse erythema with poikiloderma and heliotrope erythema. Furthermore, Muscle weakness in the extremities, especially in the lower extremities and dysphagia were observed. Magnetic resonance imaging showed nodules with a dark star sign suggesting muscular sarcoidosis in the muscles of both thighs, but not in the pharynx. CT and gastrointestinal endoscopy did not find any malignancies. Serum LDH, aspartate aminotransferase, aldolase, and sIL-2R levels were elevated; however, CK level was normal. Serum anti-SAE antibodies were identified using immunoprecipitated western blots. We diagnosed the patient with anti-SAE antibody-associated DM with sarcoidosis. The histological findings at the first visit could be explained by the fact that the skin manifestations of DM were accompanied by sarcoidosis due to the Koebner phenomenon.

After treatment with oral prednisolone 30 mg/day, the skin lesions and muscle weakness improved. Dysphagia did not improve significantly, although it did not worsen.

Although there are few reports of DM associated with sarcoidosis, the literature has been increasing in recent years. In some cases, there were intervals of more than 10 years between the first episode diagnosed as DM and sarcoidosis. They have common or similar symptoms. Sato et al.³ emphasizes that measurement of anti-CADM140/MDA5 antibody was useful to distinguish sarcoidosis from CADM with rapidly progressive interstitial lung disease. In our case, anti-SAE antibody helped us to convince that the patient had not only sarcoidosis but also DM. The etiology of DM and sarcoidosis remains unclear. CD4+ T cells and B cells may be important cofactors. Sarcoidosis is thought to be caused by an association between antigens, macrophages and CD4+ T cells which interact with B cells to stimulate antibody production⁴. In DM, the predominant lymphocytes are B cells and CD4+ T cells. Cytokines and chemokines related to complement activation facilitate the egress of activated T cells to the perimysial and endomysial spaces⁵. Further case accumulation is needed to clarify the precise underlying mechanisms.