| | Associations | Genetic associations (ref) | Clinical association (ref) |
| | SLE, SS, T1D | Shared risk genes
(i) IL2–IL21 (rs6822844) [24]
(ii) PTPN22 (1858T/C) [25, 26]
(iii) 8.1 Ancestral Haplotype [30]
(iv) TNF-α (-308G/A) [31–33] | Common clinical characteristics
(i) Human endogenous retroviruses (HERVs) are associated with multiple ADs including SLE, SS, and T1D [27]
(ii) Coexistence of SLE and SS has been reported [28, 29]
(iii) Hepatitis C virus has been related to ADs such as RA, AIH, T1D, SLE, SS, and others [40]
(iv) AIH was found in 0% to 1.7% of patients with SS. However, the prevalence of abnormal liver function test in SS patients is close to 47% [41]
(v) High prevalence of ADs in siblings of probands affected by AITD, MS, RA, T1D, SLE, and others ADs [42] | | AIH, RA, T1D | Shared risk genes
(i) DRB1*04:05 [34–36]
(ii) CTLA4 [37–39] |
| | MS, T1D | Shared risk genes | Common clinical characteristics | | (i) CD226 (rs763361), CLEC16A (rs12708716), SH2B3 (rs3184504) [43, 44]
(ii) ZSCAN23 (rs11752919) [45] | (i) A latitudinal gradient characterizes both diseases. MS and T1D each become increasingly common as distance from the Equator increases [43] | | (iii) KIF5A (rs1678542), SH2B3 (rs3184504), CD226 (rs763361) [46] | (ii) Protective effect of vitamin D levels [43]
(iii) Association to Epstein-Barr virus infection [43]
(iv) Both MS and T1D are characterized by T cell-mediated autoimmunity. The targets of T cells are pancreatic islet and central nervous system antigens in both diseases [43]
(v) Familial aggregation [47, 48] | | Shared protective genes:
(i) HLA-DRB1*01, HLA-DRB1*10, HLA-DRB1*11, and HLA-DRB1*14 [43]
Opposite gene associations:
(i) Risk for T1D but protection for MS [45]: TAP2 (rs10484565), VARS2 (rs1264303), CDSN (rs1265048), NOTCH4 (rs2071286), BTNL2 (rs2076530), TRIM40 (RS757262)
| | (ii) Risk for MS but protection for T1D [45, 49]: CDSN (rs3130981), HLA-DMB (rs151719) IL2RA (rs35285258), IL2RA (rs7090530) |
| | AIH, T1D | Shared protective alleles | Controversial characteristics | | (i) DQB1*03:01 [11, 50]
Controversial genetic and clinical characteristics:
(ii) In children with AIH, the frequency of high-risk HLA DQB1*03:02 or DQB1*02 alleles was low and similar to control frequencies, indicating low risk for DM despite the presence of DM-related autoimmunity markers [51] | (i) One case report with Grave’s disease, AIH and T1D [52]
(ii) One cohort of 278 patients with AIH presented only two cases of T1D [53]
(iii) One study reported that the prevalence of ICA and IAA antibodies in children with AIH was 60.7 and 18.5% respectively. However, only one patient developed T1D [51] |
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