BACKGROUND: Clinically amyopathic dermatomyositis (CADM) is characterized by typical skin lesions with no (amyopathic) or subclinical (hypomyopathic) evidence of muscle involvement. Patients with CADM may also develop rapidly progressive interstitial lung disease (ILD), and have a poor prognosis. However, the diagnosis of rapidly progressive ILD faces a challenge during the severe acute respiratory syndrome coronavirus 2 pandemic. Severe acute respiratory syndrome and ground-glass attenuation on a chest computed tomography scan are the presenting features in both conditions.
METHODS: A 45-year-old woman with amyopathic dermatomyositis had acute onset of fever and dyspnea in February 2020. She had abnormal lung findings on CT scan. Polymerase chain reaction testing for SARS-CoV-2 was not available at that time. Chest CT revealed non-specific manifestations that could be either the signs of ILD or SARS-CoV-2 infection. Antiviral therapy was initiated with oseltamivir. Three days later, she had erythema on face, palm, and back. The ratio of lactate dehydrogenase (LDH) isoenzyme 3 to total LDH was elevated. The ratio of LDH isoenzyme 1 to total LDH was declined. Therefore, she was transferred to the rheumatology ward for further treatment. However, she died from respiratory failure 2 weeks later.
CONCLUSIONS: We speculate that the altered LDH isoenzyme pattern may be an early biomarker for co-occurrence of CADM and ILD.

Hypomyopathic dermatomyositis (DM) presents with cutaneous lesions consistent with dermatomyositis but in the absence of clinically appreciable muscle weakness. The cutaneous manifestations are often refractory and more resistant to conventional therapy than concomitant muscle involvement. We present a 61-year-old hypomyopathic patient with DM who failed to respond to standard therapy but was successfully treated by low-dose interleukin-2 (IL-2) with no significant side effects. We conclude that low-dose IL-2 is a safe and effective treatment for hypomyopathic DM.