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.