DISCUSSION
We diagnosed an older patient with rapidly progressive finger necrosis and late-onset ARS syndrome who tested positive for anti-OJ and Ro-52 antibodies. The occurrence of ARS syndrome with positive anti-OJ antibodies is extremely rare, and reports of clinical manifestations of severe necrosis of the hands without significant interstitial pneumonia are limited.8 Additionally, the commonly used line immunoassay (LIA) method for measuring anti-OJ antibodies yielded false negative results in this case, highlighting the effectiveness of immunoprecipitation.
Ge et al.7 reported that only 10 (3.1%) of 320 patients with anti-ARS antibodies had anti-OJ antibodies. Among them, 90% had interstitial pneumonia, and 40% presented with myositis, mechanic’s hands, and arthritis. Most publications describing patients with anti-OJ antibodies have primarily focused on interstitial pneumonia8, with only one report mentioning myositis9 and none describing skin changes with necrosis. Our patient experienced mild interstitial pneumonia, while muscle weakness and necrosis of the fingers were prominent. Although the patient remained independent for activities of daily living, he faced difficulties in swallowing and lost the ability to walk after just 1 month. Finger necrosis was notably absent upon admission but progressed rapidly and intensely within 3 days.
On admission, anti-Ro-52 was strongly positive. Anti-ARS antibody syndrome typically involves anti-Ro-52 antibodies, and these are associated with a poor prognosis when anti-ARS antibody syndrome occurs along with concomitant interstitial pneumonia.10Anti-Ro-52 antibodies are found in up to 37% of patients with myositis, and this often correlates with anti-Jo-1 reactivity.1This, together with the clinical presentation, indicated myositis involvement. However, anti-Jo-1 and anti-ARS antibodies were all negative. Few reports have described finger necrosis due to myositis, and we considered the possibility of a paraneoplastic acral vascular syndrome.12 Consequently, we requested a test for anti-U5snRNP antibody, which was negative. Nevertheless, we retested anti-OJ antibody by immunoprecipitation, which was positive.
We considered initiating PSL at a dose of 1 mg/kg for the patient while awaiting the examination results. However, because of the sudden deterioration of the patient’s respiratory status, (necessitating the administration of 10 min of masked oxygen), and the possibility of exacerbation of the interstitial pneumonia, we opted for methylprednisolone pulse treatment. Imaging revealed a mildly exacerbated interstitial shadow, without elevated KL-6 or SP-D. He also had a history of chronic obstructive pulmonary disease as a cause of worsening respiratory status, which was thought to be due to CO2 narcosis. After administering the methylprednisolone pulse, the expanding necrotic lesion, which had shown no signs of prior improvement, exhibited a purple transition zone at the border between the normal skin and black necrotic area (Fig. 1C). Subsequently, the expansion of necrosis halted. The pathogenesis of finger necrosis in anti-ARS syndrome has been documented. For example, Chan et al.13 reported a PL-7(+) case where conventional angiography revealed occlusion of the second to fourth fingers. Suma et al.14 reported Jo-1(+) anti-ARS antibody (+) mechanistic hand, with peripheral angiography revealing occlusion of both the ulnar and radial arteries. Linear hemorrhage of fingernails accompanied by digital ischemia or digital ulcer in anti-ARS syndrome has also been reported.13–15In our case, no obvious stenosis or occlusion was observed on contrast-enhanced CT angiography, and there was no linear hemorrhage of the nails. However, we observed extreme necrosis, which was unprecedented in our experience. Nonetheless, the presence of necrosis would typically suggest ischemia caused by blood flow obstruction in the vessel, which may be a limitation of CT angiography. Furthermore, because of the patient’s intubation and poor general condition, angiography was not performed. Although the patient had no history of Raynaud phenomenon, spasms of the peripheral arteries in the fingers might have contributed to the significant necrosis. However, there are \soutno few reports of digital necrosis in patients who are positive for anti-OJ antibodies. Lastly, muscle strength showed significant improvement after PSL administration, showing the efficacy of PSL pulses in these patients.
The limited number of reports may be attributed to the rarity of this condition and challenges in testing. Anti-OJ antibodies are difficult to detect among all myositis-specific antibodies. Unlike other tRNA synthetase targets of autoantibodies, including Jo-1, PL-7, PL-12, KS, EJ, and Zo, OJ antibodies are complex high-molecular-weight proteins with several subunits, posing challenges for antigen selection.16 The LIA method has lower sensitivity in detecting anti-OJ antibodies.17–19 However, it is still widely applied in clinical practice owing to the lack of alternative methods and its ease of use, despite the superior diagnostic performance of advanced immunoprecipitation methods.20, 21 In this case, although the patient initially tested negative for anti-OJ antibodies using the LIA method, he tested positive based on the immunoprecipitation method. The single enzyme-linked immunosorbent assay kit commonly used for the anti-ARS antibody assay no longer detects anti-Zo and anti-Ha antibodies, as they have only been reported in isolated cases.
If clinicians suspect the presence of anti-OJ antibodies and myositis and finger necrosis are more prominent than symptoms of interstitial pneumonia, a diagnosis should be confirmed through immunoprecipitation.