**Genetic Factors**

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50 Sarcoidosis

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**Chapter 3**

**Genetic Factors Involved in Sarcoidosis**

Sarcoidosis is an immune mediated disease thought to be caused by complex interaction between genetic and environmental factors. Involvement of genetic factors in sarcoidosis is supported by familial clustering, increased concordance in monozygotic twins and varying incidence and disease presentation among different ethnic groups. Studies have revealed several human leukocyte antigen (HLA) and non-HLA alleles consistently associated with sarcoidosis susceptibility. Two genome scans have been reported in sarcoidosis: one in African Americans reporting linkage to chromosome 5 and the other in German families reporting linkage to chromosome 6. Follow-up studies on chromosome 6 identified the BTNL2 gene, a B7 family costimulatory molecule to be associated with sarcoidosis. Recent genome-wide association studies have found annexin A11 and RAB23 genes associated with sarcoidosis. The ongoing refinement of genetic marker maps, genotyping technology, and statistical analyses

Familial sarcoidosis was first noted in Germany in 1923 by Martenstein, who reported two affected sisters [1]. After that several familial cases were reported across Europe and USA. Worldwide surveys revealed that familial sarcoidosis occurred in 10.3% cases from the Netherlands [2], 7.5% from Germany [3], 5.9% from the United Kingdom [4], 4.7% from Finland [5], 4.3% from Japan [5], 9.6% from Ireland[6] and 6.9 % from Sweden[7]. A family history survey of Detroit clinic–based population in USA showed that 17% of African Americans and 3.8% of white American reported a family history in first- and second degree relatives[8]. In African Americans, the sibling recurrence risk ratio, which compares disease risk among

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© 2013 Sah and Iannuzzi; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

Birendra P. Sah and Michael C. Iannuzzi

http://dx.doi.org/10.5772/55116

**1. Introduction**

Additional information is available at the end of the chapter

makes genomic exploration for sarcoidosis genes appealing.

**2. Evidence for genetic predisposition to sarcoidosis**
