Updated publication reference for PubMed record(s): 31296869. Lamins are intermediate filament proteins responsible for nuclear mechanical integrity. Though linked to multiple heritable diseases, lamin structure and that of other intermediate filaments remains elusive. We employed cross-linking mass spectrometry to gain structural insights into lamin A dimer and tetramer structure. While confirming the parallel coiled-coil rod, we report that, contrary to prediction, rod linker regions are highly flexible and compressible. This explains the recently reported rod shortening in the assembled polymer and aspects of intermediate filament stretch properties. We further elucidate an extended interface in lamin A tetramers where both head and tail unstructured regions flanking the rod of each dimer act as polar bridges to stabilize lamin head-to-tail assembly. Furthermore, changes in these regions between dimer and tetramer forms suggest an ordered polymer assembly. Importantly, several residues mutated in laminopathies disrupt this interface and impair assembly, potentially explaining their role in disease.