BACKGROUND: Despite the advancements in the categorization of clinically amyopathic dermatomyositis (CADM), the classification and diagnosis of its subtypes are still challenging. The aim of our study was to describe the clinicopathological features of CADM and assess the differences between amyopathic dermatomyositis (ADM) and hypomyopathic dermatomyositis (HDM).
METHODS: This retrospective study included 43 patients with CADM diagnosed at our institution from 2016 to 2020. Patients were subclassed into ADM (n = 30) and HDM (n = 13) groups to assess their clinicopathological differences.
RESULTS: All included patients had characteristic cutaneous manifestations of dermatomyositis; 67.4% had myositis-associated auto-antibodies, including ANA (32.6%), RNP (14.0%), anti-Ro52 (9.3%), anti-p155/140 (7.0%), rheumatoid factor (7.0%), anti-NXP-2 (4.7%), anti-MDA5 (2.3%), and anti-Jo-1 (2.3%) antibodies. One patient had associated interstitial lung disease, and another patient had oral squamous cell carcinoma. The histopathological findings included mucin deposition (69.8%), telangiectasia (65.1%), lymphocytic infiltrate (48.8%), vacuolar interface dermatitis (46.5%), and epidermal atrophy (14.0%). Compared to patients with HDM, ADM patients were significantly less likely to have epidermal atrophy, 3.3% versus 38.5% (p = 0.006), and more likely to have mucin deposition, 80.0% versus 46.2% (p = 0.028).
CONCLUSIONS: We described the clinicopathological features of CADM and highlighted the distinctions between ADM and HDM dermatopathologic findings. This information may prove helpful in diagnosing ambiguous lesions.

Overlap syndrome is a clinical challenge and brings together a wide range of treatment options for the treating physician. Addressing each and every complaint of the patient is crucial. A 50-year-old female patient presented with skin thickening, blackening, and hyperkeratosis; dysphagia; joint pain; features of myopathy; Raynaud\'s phenomenon; and dry mouth. Inflammatory markers were raised along with a positive antinuclear antibody (ANA) with Golgi apparatus pattern, anti-Sjögren\'s-syndrome-related antigen A (anti-SSA)/Ro60 3+, anti-SSA/Ro52 3+, and anti-PM/Scl 2+ antibodies that suggested overlap syndrome. Although the patient had no respiratory complaints, a unique interstitial lung disease (ILD) pattern was noted during the evaluation. Skin manifestations were puzzling, but the histopathology analyses of skin biopsies taken from two different sites revealed distinguishing features of cutaneous lupus and dermatomyositis. Treatment with hydroxychloroquine, pilocarpine, nifedipine, methotrexate, and topical tacrolimus produced a dramatic improvement in the clinical features. This case highlights subtle and florid features of different autoimmune diseases. The hyperkeratotic skin changes were the most striking feature, but the whole evaluation process unveiled many rare presentations of known autoimmune conditions that can open doors to new areas of our understanding toward connective tissue diseases (CTDs). Our case report demonstrates significant heterogeneity in the ANA patterns, ILD patterns, clinical manifestations, and treatment approaches.

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.

Dermatomyositis is associated with malignancies and is known to have systemic involvement. However, associations with bone diseases have not been well described in the current literature. This article describes the second reported case of the co-existence of dermatomyositis and Paget\'s Disease of Bone (PDB), but is the first report to describe such co-existence in a specific subtype of dermatomyositis - hypomyopathic dermatomyositis. Our patient was a 51-year-old woman who presented with prolonged fever, myalgia, morning stiffness, and rashes pathognomonic of dermatomyositis. There was no muscle weakness clinically, although muscle enzymes were raised and electromyogram revealed myopathic changes. Further imaging showed the incidental finding of a T11 vertebral bone lesion, of which biopsy confirmed the diagnosis of PDB. Our report illustrates the diagnostic approach to bone lesions in patients with dermatomyositis, and takes a closer look at the pathophysiology and management implications of the co-occurrence of these two rare diseases.

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.

A 47-year-old Haitian male with no known past medical history was admitted to the hospital for gradually progressive dyspnea, nonproductive cough, and weight loss. He also endorsed a one-year history of joint pains. He was febrile and tachycardic and in mild respiratory distress. Other pertinent physical examination findings included diffuse inspiratory crackles, digital ulcers, and symmetric swelling of the wrists, elbows, shoulders, and knees. He was found to have a right basilar consolidation on chest computed tomography (CT) and was placed on antibiotics for presumptive pneumonia. His CD4 count was 158 cells per microliter despite testing negative for human immunodeficiency virus (HIV). A thorough infectious workup was unrevealing, and he did not improve with antibiotics. He had a weakly positive anti-nuclear antibody (ANA) with an otherwise negative rheumatologic workup. Creatinine kinase and aspartate aminotransferase were mildly elevated in the absence of overt muscle weakness. A myositis panel, including melanoma differentiation-associated protein five (anti-MDA5) antibody, was negative at the time. He was discharged on a short course of prednisone without a definitive diagnosis. He returned several months later with worsening respiratory symptoms. At this time, a lung biopsy revealed interstitial lung disease. Repeat myositis panel demonstrated anti-MDA5 positivity. The patient was also found to have new-onset non-ischemic heart failure with reduced ejection fraction. A diagnosis of hypomyopathic dermatomyositis was made based on clinical, laboratory, and imaging findings. The patient was restarted on prednisone, and mycophenolate mofetil was subsequently initiated for maintenance therapy.