Medical vision-language models are typically trained by aligning whole images with entire radiology reports, assuming that global correspondence is sufficient for learning clinically meaningful representations. We argue that effective medical representation learning requires pathology-localized supervision, which explicitly aligns specific disease observations with their corresponding anatomical image regions. To enable this at scale, we propose a fully automated pipeline that decomposes radiology reports into atomic disease observations, identifies relevant regions, and pairs them with corresponding image regions without manual annotation, resulting in a fine-grained dataset, LocalizedCXR, with over 6 million region–caption pairs. Through extensive experiments, we demonstrate that our pathology-localized semantic supervision significantly improve performance in cross-modal retrieval, image classification, and phrase grounding of radiology findings. Our results suggest that moving beyond global alignment to disease-aware region-level alignment is essential for developing effective medical vision-language representation learning.