Autoantibodies in patients with
myositis may associate with specific clinical manifestations. This study aimed to identify a subset of patients with
myositis carrying antinuclear matrix
protein 2 (anti-NXP-2)
antibodies using an unlabeled immunoprecipitation (IP) assay, and clarify the features of these patients in a Chinese cohort. We developed novel methods for unlabeled
protein IP and immunoblotting of Myc-tagged truncated NXP-2 fragments for anti-NXP-2 detection. The sera of 120 Chinese adult patients with
myositis were screened for anti-NXP-2 by IP and immunoblot. Anti-NXP-2
antibodies were detected in 10 of the 120 patients (8.3%) using the established unlabeled
protein IP and immunoblotting, with 70% (7/10) exhibiting either heliotrope
rash or Gottron's papules. All 10 anti-NXP-2-positive patients exhibited
myopathy and 60% complained of
dysphagia. Severe diffuse
calcinosis (10%) and
nasopharyngeal carcinoma (10%) were each only present in single anti-NXP-2-positive patients with
myositis.
Antibodies against Ro-52 were found in four living but not in three deceased anti-NXP-2-positive patients. A comprehensive review of 13 anti-NXP-2 studies demonstrated markedly lower anti-NXP-2 prevalence among adult patients with
myositis and lower association of anti-NXP-2 with
calcinosis in Japan, China, and Hungary than in the USA and Italy. Anti-NXP-2 antibody association with internal
malignancy in adult patients varied from 0 to 50% across different studies. A novel IP assay was developed to detect patients with
myositis expressing anti-NXP-2.
Calcinosis and
malignancy are rare in Chinese adult patients with
myositis positive for anti-NXP-2. Literature review indicated highest anti-NXP-2 prevalence and association of anti-NXP-2 with
calcinosis in US and Italian
myositis cohorts.