Objective　To investigate the characteristics and essential points of diagnosis and treatment of double trisomy 47，XXX/48，XXX，+8 combined Behcet disease, a rare inherited immunodeficiency disorder. Methods　The clinical manifestations, karyotype analysis and gene test results of the patients were analyzed, and relevant literatures were reviewed. Results　A 11-year-old girl presented repeated fever for more than 6 years, accompanied with recurrent genital herpes infection and oral apthosis, was clinically diagnosed with Behcet disease. Cytogentic and molecular karyotyping on peripheral lymphocytes demonstrated 47，XXX[12]/48，XXX，+8[18]. Conclusions　Conventional karyotype analysis and chromosomal microarray analysis have a complementary role in the diagnosis of the disease. We conclude that patients with constitutional trisomy 8 and those with trisomy 8 confined to the bone marrow are both at increased risk of developing features of Behcet disease. The mechanism may relate to increased gene dosage of candidate genes for  Behcet’s disease on chromosome 8.