Quercetin in Patients With XIAP (X-linked Inhibitor of Apoptosis) Deficiency

Inclusion Criteria: * Male patients * Diagnosis of XIAP deficiency * Patients ≥2 years of age * Serum IL-18 ≥600 pg/mL (approximately 25% above the lab-defined upper limit of normal of 477 pg/mL) * Able to take enteral medication Exclusion Criteria: * Renal failure requiring dialysis * Total bilirubin \>3 mg/dl and/or SGPT \>300 at time of enrollment * Patients receiving digoxin therapy, who are unable to discontinue treatment due to medical reasons * Patients receiving fluoroquinolone therapy, who are unable to discontinue treatment due to medical reasons * Patients who are at risk of pregnancy or fathering a child and are unable to use acceptable methods of birth control during the length of the study * Patients who have received quercetin or any over the counter anti-oxidant supplementation within last 1 month * Patients with unstable disease status or other medical issues requiring hospitalization or rapid escalation of medical care * Participating in another therapeutic study for XIAP deficiency