Va riation in BTNL8. (A) MTR across ancestral groups calculated using gnomAD 2.1.1 data. An MTR of 1 corresponds to selective neutrality, with lower values indicating intolerance to missense variation. (B) Schematic of BTNL8 protein domains aligned to the coordinates of the MTR plot. (C) Theoretical power calculation for the BTNL8*3 CNV. Assuming a CNV AF of 26%, a large control group derived from gnomAD (100,000 individuals) and an exome-wide significance threshold of 2.5 × 10⁻⁶, the plot depicts the required sample size at different effect size levels. At least 1,380 MIS-C cases would be required to achieve 80% power of detecting a 2.5 OR.