A Clinical Case of Polymyositis Complicated by Antisynthetase Syndrome

Abstract

Antisynthetase syndrome is an autoimmune condition that manifests clinically through signs and symptoms, such as interstitial lung disease, myositis, Raynaud’s phenomenon, fever, hyperkeratotic fingertips (mechanic’s hands), and arthritis. It is associated with antibodies against aminoacyl tRNA synthetase enzyme, the most common autoantibody being the anti-Jo-1. An 18-year-old girl presented with weakness of both the upper and lower limb, swelling and generalized body pain, difficulty in swallowing. MRI of the thigh was highly suggestive of myositis with symmetrical bilateral involvement. Based on proximal muscle weakness, elevated creatine phosphokinase (CPK), and lactate dehydrogenase (LDH), strongly positive anti-nuclear antibodies human epithelial cell type-2 (ANA-HEp2), and a normal nerve conduction velocity test with precise MRI findings, a diagnosis of polymyositis was made. She was given bolus intravenous methylprednisolone for five days, followed by oral methylprednisolone with subcutaneous methotrexate weekly. She reported a 50% improvement in muscle weakness; however, partial bulbar weakness persisted at the time of discharge. On her next follow-up, her blood investigations for auto-antibodies were done. The autoantibodies anti-Jo-1 (3+), Ro-52 (2+), and Mi-2β (2+) were found to be positive. These investigations, coupled with the clinical features she was presenting, finally led us to conclude that it was a case of polymyositis complicated by the antisynthetase syndrome.

Anti-synthetase Syndrome: A Diagnostic Dilemma

“…ASS is a rare autoimmune disorder with heterogenous clinical manifestations overlapping with those of other rheumatoid diseases. Different patients may present with distinct clinical patterns and the symptoms and signs may develop or change gradually over the course of the disease, thus, making it difficult to timely diagnose and manage patients with this condition [ 5 ]. Its most common clinical features include interstitial lung disease, myositis, and arthritis.…”

“…ASS is closely related to dermatomyositis and polymyositis with interstitial lung disease and arthritis [ 2 ]. The prevalence is still unknown, and the disease more commonly affects females with a female-to-male ratio of 3:1 [ 5 ]. The literature suggests that human leukocyte antigen (HLA) DRB1*0301, DQA1*0501, and DQB1*0201 genes are common risk factors for the development of ASS [ 2 ].…”

“…The common clinical presentations of ASS, which include myositis, interstitial lung disease, arthritis, Raynaud’s phenomenon, and mechanic's hands [ 5 ], overlap with other more common autoimmune rheumatic diseases leading to diagnostic confusion. Some patients may also have symptoms of dry eyes, dry mouth, and difficulty swallowing, features overlapping with Sjogren’s syndrome and systemic sclerosis [ 6 ].…”