Genetic analysis revealed a Factor V Leiden gene variation (c.4192A>T, p.Ser1398Cys) and the diagnosis of resistance to activated protein C. Case 6, an 11 years old, was diagnosed as DVT of bilateral limbs and pulmonary embolism, LA, and aβ2GPI‐IgM were positive. The gene discussed is F5; the disease is deep vein thrombosis.