PMC6649910_01
Chest CT images and immunoprecipitation analysis. (A) Chest CT images from 2001 (disease onset), 2005 (second flare-up), 2014 (clinically stable period) and 2016 (on admission). (B) RNA immunoprecipitation assay with patient sera. Lane 1, total RNA; lane 2, serum from 2001; lane 3, serum from 2005; lane 4, serum from 2016; lane 5, positive control serum for anti-EJ antibody. (C) Immunoprecipitation of polypeptides with patient sera. Lane 1, molecular marker; lane 2, serum from 2001; lane 3, serum from 2005; lane 4, serum from 2016; lane 5, positive control serum for anti-MDA5 antibody; arrow, anti-MDA5 antibody (140 kDa); arrowhead, anti-EJ antibody (75 kDa). (D) Chest CT images on admission and 7 weeks later. EJ: glycyl-tRNA synthetase; MDA5: melanoma differentiation-associated gene 5.
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Chest CT showed newly developed peripheral random ground-glass attenuation (GGA), marked reticulation, traction bronchiectasis and volume loss in the lower lung field bilaterally (Fig. 1A).  Although anti-EJ antibody had been detected twice previously, RNA immunoprecipitation on admission was negative (Fig. 1B). We retrospectively screened frozen sera from 2001 and 2005, identifying anti-MDA5 antibody in both samples by ELISA and protein immunoprecipitation (Fig. 1C). Follow-up chest CT at the time showed newly developed random GGA (Fig. 1D).