An Unusual and Rare Presentation of Dermatomyositis Sine Dermatitis Complicated by Neuromyositis

Abstract

Dermatomyositis sine dermatitis (DMSD) is a rare autoimmune disease. It's distinguished from classical dermatomyositis (DM) by a lack of skin involvement. DM is known to have a variety of extramuscular manifestations, including interstitial lung disease, myocarditis, and dysphagia. However, peripheral nervous system involvement in DM termed "Neuromyositis" is less often encountered. Neuromyositis diagnosis is controversial due to its rarity, unknown mechanism, and heterogeneity of nerve pathology findings. A 53-year-old woman presented to our hospital following a fall. Six months prior to presentation, she had a sensory disturbance in her right foot. On admission, she had a right foot drop that progressed to right then left lower extremity weakness. A biopsy of the superficial peroneal nerve and long peroneal muscle showed large fiber nerve axonal loss, CD20 B-cell and CD4 T-cell predominant inflammatory infiltrate involving the perimysial connective tissue of the muscle, as well as myocyte hypertrophy and fibrosis with type I fiber predominance. These findings were compatible with dermatomyositis with neuropathic features. Electrophysiological studies of lower extremities revealed severe widespread axonal dysfunction, as evidenced by decreased tibial compound muscle action potential (CMAP), no peroneal motor responses, absent sural sensory nerve action potential (SNAP), and extensive active denervation throughout the left lower extremity. Three months later, she developed bilateral upper extremity weakness. A biopsy of the deltoid muscle that was done eight months after admission showed CD20 B-cell and CD4 T-cell predominant inflammatory infiltrates involving the perimysial connective tissue. These findings were pathologically similar to the first biopsy. Subsequently, a repeat electromyography (EMG) of upper extremities revealed myopathic changes with normal nerve conductions. She ultimately became quadriplegic and ventilator-dependent nine months after admission. She never exhibited any skin findings throughout her course of illness. An extensive imaging and laboratory workup did not reveal any occult malignancy, inflammation, or nutritional deficiency. Our patient did not respond to steroids or intravenous immunoglobulin (IVIg) and ultimately passed away. The clinical, pathological, and electrophysiological features suggested the presence of neuromyositis. This case illustrates the importance of recognizing peripheral nervous system involvement as a significant and yet underreported extramuscular manifestation of DM. There are currently no formal management guidelines for neuromyositis.

A Case Report on Rare Presentation of Sporadic Disease: Dermatomyositis Sine Dermatitis—Diagnosis and Management

“…Dermatomyositis has different types based on muscle and skin, and only muscle or skin involvement. 1 Dermatomyositis sine dermatitis is diagnosed when only muscle weakness is present without any skin symptoms, such as Gottron’s papule and heliotrope rash, muscle biopsy changes, and muscle antibody suggestive of DMSD, which was seen in our patient. Anti-MDA5 antibody is one of the specific antibodies to DM and is more specific to amyopathic DM than DMSD; also, patients with DMSD who have anti-nuclear matrix protein 2 [NXP-2] positive show more specific antibody marker for DMSD than any other subtypes of DM.…”

“… 1 , 2 The anti-MDA5 antibody in DM patients correlates with the severity of lung disease in terms of ILD, respiratory muscle weakness with poor outcome, and an inadequate response to immunosuppressive therapy. 1 , 4 …”

“…The patient presents with symptoms of skin rash, muscle weakness, and extra muscular involvement, such as dysphagia, interstitial lung disease (ILD), and myocarditis.1 Based on clinical presentation, DM is classified into 3 categories: (1) classic DM with skin and muscle symptoms, where patients usually have proximal muscle weakness associated with skin rashes such as Gottron’s papules and heliotrope rash; (2) amyopathic DM, where the patient presents with skin symptoms without any muscular involvement or weakness. 1 In contrast, (3) dermatomyositis sine dermatitis (DMSD) has myopathy symptoms with muscle antibodies but no skin rashes. 1 However, DMSD usually has anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibody-positive, ILD, and also accounts for poor prognosis.…”

“… 1 In contrast, (3) dermatomyositis sine dermatitis (DMSD) has myopathy symptoms with muscle antibodies but no skin rashes. 1 However, DMSD usually has anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibody-positive, ILD, and also accounts for poor prognosis. 1 Here, the patient presented with symptoms of DMSD but without any lung involvement and showed an excellent response to steroids.…”

“… 1 However, DMSD usually has anti-melanoma differentiation-associated gene 5 (anti-MDA5) antibody-positive, ILD, and also accounts for poor prognosis. 1 Here, the patient presented with symptoms of DMSD but without any lung involvement and showed an excellent response to steroids. Around 8% of DM accounts for DMSD confirmed with muscle biopsy.…”