Anti-synthetase Syndrome: A Diagnostic Dilemma

Abstract

Among the various inflammatory myopathies, the anti-synthetase syndrome (ASS) is a rare entity with autoantibodies directed against aminoacyl-transfer ribonucleic acid synthetase. Its clinical spectrum ranges from myopathy and non-erosive arthritis to dyspnea and cough of pulmonary interstitial disease and from hyperkeratotic skin changes to spasms of blood vessels causing Raynaud's phenomenon. We present a case of a 21-year-old female who had been suffering from fever, night sweats, and weight loss for two years and had remained undiagnosed. She came to our hospital with new-onset muscle weakness, small joint arthralgia, and skin changes. Physical examination showed inflammation involving multiple small joints and characteristic hyperkeratotic skin changes in the distal and lateral phalanges of the hands and feet. Raised creatine phosphokinase levels indicated the possibility of myositis along with positive anti-nuclear antibodies, suggesting an autoimmune rheumatic disorder. Inflammatory myositis was later confirmed on biopsy. Further investigations revealed positive anti-Jo1 antibodies. The diagnosis of ASS was made despite the absence of pulmonary signs and symptoms. The patient was promptly started on prednisone and azathioprine. She showed some improvement in muscle weakness at the end of two months and continues to improve albeit slowly. Due to the lack of awareness about the rare disease among the non-rheumatologists, there was a significant delay in the patient's diagnosis. It is, therefore, important for primary care physicians to obtain a comprehensive history and perform a detailed clinical examination to make timely referrals to specialized healthcare professionals.

Keywords: anti-jo1 antibodies; anti-synthetase syndrome; inflammatory myopathy; non-erosive arthritis; polymyositis.

Figure 1. Hand X-ray

X-ray showing normal symmetrical joints without bone overlapping except at the carpal and base of the metacarpal bones. No fractures, osteopenia, or bone deformities were noted.

Figure 2. Mechanic's hands

Image showing a nonpruritic, hyperkeratotic, and scaly eruption on the ulnar side of the thumb and radial side of other fingers, fingertips, and base of the nail bed.

Figure 3. Hiker's feet

Image showing hyperkeratosis and cracking of the skin of the toes.