We have used this technique to collect and ship DBS from a number of South American countries to identify disease-causing mutations in >25 PID-associated genes including WAS, CD40L, PIK3CD, FOXP3, CTLA4, STAT1, STAT3, RAG1, and RAG2. Because of the limited quantity of patient material, we had to slightly modify the PCR amplification technique that we routinely use for gDNA extraction from peripheral blood or saliva. Here, FOXP3 is linked to pelvic inflammatory disease.