EIF2AK4 encodes general control nonderepressible 2 kinase (GCN2), a stress-responsive serine/threonine protein kinase that regulates translational initiation through eIF2α phosphorylation 1. The kinase responds to amino acid starvation and ribosome stalling events triggered by translation perturbations, activating stress response pathways including GCN2-mediated signaling and SAPK cascades 2. During amino acid deprivation, GCN2 promotes dendritic cell autophagy and antigen presentation, contributing to adaptive immune responses against pathogens 3. In response to DNA damage, GCN2 mediates global translation inhibition and apoptosis through ribosome stalling pathways 4. Clinically, biallelic EIF2AK4 mutations cause pulmonary veno-occlusive disease (PVOD), a severe form of pulmonary hypertension characterized by small pulmonary vein and capillary remodeling 5. In non-hereditary pulmonary arterial hypertension, GCN2 kinase activation promotes vascular remodeling and disease progression through endothelin-1 signaling 1. EIF2AK4 is classified with definitive evidence for causative PAH/PVOD gene-disease relationships 6, making it clinically important for genetic testing in heritable pulmonary hypertension. PVOD patients face poor prognosis and risk of life-threatening pulmonary edema with standard PAH therapies, necessitating early lung transplant referral 7.