This is a clinical trial to study the use of Tadekinig alfa or placebo (medication) in the treatment of NLRC4 MAS mutation or XIAP deficiency. This study involves taking the medication every 48 hours for up to 26 weeks. Participants will also be required to attend up to 14 in-person study visits to review their disease state while they are taking the medication. Compensation for time and travel related to study visits may be provided to qualified participants.