AC-20 - Cytoplasmic fine speckled
Previous Nomenclature cytoplasmic speckled
Description Scattered small speckles in the cytoplasm mostly with homogeneous or dense fine speckled background. e.g. anti-Jo-1.
Antigen Association Jo-1/histidyl-tRNA synthetase
Clinical Relevance
First level information
About Clinical Relevance & List of Abbreviations

Found in patients with the anti-synthetase syndrome (a subset of AIM), interstitial lung disease, polyarthritis, Raynaud’s phenomenon, and mechanic’s hands; these features may occur in various combinations or as an isolated manifestation, especially interstitial lung disease (33, 90)

Autoantibodies associated with the AC-20 pattern are primarily reported for the anti-Jo-1 antibody, which recognizes histidyl-tRNA synthetase; since AC-20 is not specific for Jo-1, it is recommended to perform a follow-up test for anti-Jo-1 antibodies; the antigen is included in the routine ENA profile, as well as in disease specific immunoassays (i.e., inflammatory myopathy profile*); the anti-Jo-1 antibodies are included in the classification criteria for AIM (91, 92)


Notes: The fine distinction between AC-19 and -20 may depend on HEp-2 substrates and/or antibody concentration; antibodies to Jo-1 may be undetected in HEp-2 IIFA-screening.


*Availability of the inflammatory myopathy profile, the SSc profile and the (extended) liver profile may be limited to specialty clinical laboratories.

First level information references
Satoh M, Tanaka S, Ceribelli A, et al. A comprehensive overview on myositis-specific antibodies: new and old biomarkers in idiopathic inflammatory myopathy. Clin Rev Allergy Immunol 2017;52:1-19.
Marie I, Hatron PY, Cherin P, et al. Functional outcome and prognostic factors in anti-Jo1 patients with antisynthetase syndrome. Arthritis Res Ther 2013;15.
Fritzler MJ, Choi MY, Mahler M. The antinuclear antibody test in the diagnosis of antisynthetase syndrome and other autoimmune myopathies. J Rheumatol 2018;45:444.1-5.
Lundberg IE, Tja¨rnlund A, Bottai M, et al. 2017 European league against rheumatism/American college of rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups. Ann Rheum Dis 2017;76:1955-64.
Second level information
Second level information references
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Online since 19 May 2015