Given the persistence of arthralgia, a family history of autoimmunity, and ANA +  + results, an exome sequencing test was performed, which identified the mutation c.398 T > A (p.Ile133Asn) in the PIK3R1 gene, suggesting a diagnosis of primary immunodeficiency APDS associated with the heterozygous mutation on chromosome 5q13. The gene discussed is BTG3; the disease is Autoimmunity.