Table 1

Clinical characteristics of anti-Ku patients in cluster numbers 1–3

Cluster
(n=42) C1
(n=15)
C2
(n=18)
C3
(n=9)
P value
Demographic data
 Age, years (range)39.1 (11.3–74.6)60.5 (22.6–74.3)39.1 (17.5–74.6)17.9 (11.3–64.2)0.29
 Sex (F/M)35/713/214/48/11.0
 Geographical origin (Caucasia/Africa)31/1111/414/46/31.0
Organ involvements (ever)
 Arthralgia35 (83)11 (73)15 (83)9 (100)1.0
 Raynaud’s phenomenon18 (43)9 (60)6 (33)3 (33)1.0
 Increased CK15 (35) 14 (93) 1 (6) 0 < 0.001
 Muscle weakness8 (19) 8 (53) 0 0 0.0039
 Dysphagia6 (14)6 (40)000.056
 ILD*13 (31) 13 (87) 0 0 < 0.001
 Renal involvement†10 (24) 2 (13) 1 (6) 7 (78) 0.0036
 Cytopenia13 (31) 3 (20) 1 (6) 9 (100) < 0.001
 Serositis8 (19)3 (20)1 (6)4 (44)1.0
 Lupus rash9 (21) 1 (7) 0 8 (89) < 0.001
 Telangiectasia2 (5)2 (13)001.0
 Sclerodactyly2 (5)2 (13)001.0
 Skin thickening proximal to the MCP1 (2)1 (7)001.0
 Mechanic’s hand3 (7)3 (20)001.0
 Thrombosis9 (21)5 (33)2 (11)2 (22)1.0
 Neuropathy4 (9)1 (7)03 (33)0.66
 Myocarditis1 (2)1 (7)001.0
Autoantibodies (ever)
 Anti-dsDNA‡10 (24) 2 (13) 0 8 (89) < 0.001
 Anti-SSA/Ro6013 (31)5 (33)3 (17)5 (56)1.0
 Anti-SSB/La3 (7)01 (6)2 (22)1.0
 Anti-Sm2 (5)002 (22)0.81
 Anti-RNP5 (12) 0 0 5 (56) < 0.001
 Rheumatoid factor13 (31)4 (27)9 (50)01.0
 ACPA5 (12)1 (7)3 (17)1 (11)1.0
 Antiphospholipid biology§7 (17)1 (7)1 (6)5 (56)0.064
Matched CTD criteria (at last follow-up)
 SLE8 (19) 1 (7) 0 7 (78) < 0.001
 Myositis10 (24) 10 (67) 0 0 < 0.001
 SS¶15 (36)4 (27)9 (50)2 (22)1.0
 pSS11 (26)2 (13)9 (50)00.27
 MCTD5 (12) 0 0 5 (56) < 0.001
 SSc2 (5)2 (13)001.0
 RA4 (10)04 (22)01.0
 APLS**4 (10)1 (7)1 (6)2 (22)1.0
 UCTD7 (17)2 (13)5 (28)01.0
 >1 CTD11 (26)4 (27)1 (6)6 (67)0.12
 >1 CTD (after exclusion of sSS and APLS)5 (12)2 (13)03 (33)1.0
Associated cancer††4 (10)1 (7)2 (11)1 (11)1.0
  • C1 to 3: clusters 1, 2 and 3 were identified by multiple correspondence analyses of the 28 cumulative clinico-biological features of the 42 anti-Ku patients.

  • Statistically significant results are in bold.

  • *CT scan patterns were NSIP (n=8), UIP (n=2), OP (n=2); median vital capacity was 66% (range 20–124) and transfer factor of the lung for carbon monoxide was 57% (range 15–94).

  • †Renal involvement consisted of glomerulonephritis in all cases. Kidney biopsy (available in eight patients) revealed lupus glomerulonephritis class IV (n=5), extracapillary glomerulonephritis (n=2) and proliferative glomerulonephritis (n=1).

  • ‡The titre of anti-dsDNA was 146 UI/L (56–300).

  • §Antiphospholipid biology consisted of the presence of one or more of the following laboratory criteria, on two or more occasions, at least 12 weeks apart: titre of anticardiolipin antibodies (IgG and/or IgM isotype)>40 GPL or MPL (n=4); anti-β2GPI antibodies (IgG and/or IgM isotype)>40 GPL or MPL (n=1) and/or lupus anticoagulant activity (n=4).

  • ¶Patients with sSS were listed both by sSS and by their primary connective tissue disease.

  • **APLS was secondary in all cases (no patient had primary antiphospholipid syndrome).

  • ††Associated cancer consisted of cancer diagnosed within 3 years (before or after) the diagnosis of idiopathic inflammatory myopathies.

  • ACPA, anticitrullinated peptide antibodies;APLS, antiphospholipid syndrome;CK, creatine kinase; CTD, connective tissue disease; GPL, IgG Phospholipid Units; ILD, interstitial lung disease;MCP, metacarpophalangeal joint; MCTD, mixed connective tissue disease;MPL, IgM Phospholipid Units; NSIP, non specific interstitial pneumonia; OP, organizing pneumonia; RA, rheumatoid arthritis; RNP, ribonucleoprotein; SLE, systemic lupus erythematosus; SS, Sjögren's syndrome; SSc, systemic sclerosis;UCTD, undifferentiated connective tissue disease; UIP, usual interstitial pneumonia; pSS, primary Sjögren’s syndrome; sSS, secondary Sjögren’s syndrome.