SFTPD and chronic obstructive pulmonary disease: ATP2C2, a calcium-transporting ATPase linked to surfactant protein D levels via an intronic variant (rs9927461, a causal risk factor for COPD),42 is associated with COPD in our gene-trait analyses (HR = 8.3 [95% CI = 7.54–9.05], (p < 3.56 × 10−8).