Due to the rarity of this condition, additional studies and case reports are required to better understand and manage late-onset neonatal lupus cardiomyopathies.<h4>Case presentation</h4>A 4-week-old female, born to a mother with known anti-SSA/Ro and anti-SSB/La autoantibodies, presents with classic cutaneous manifestations for neonatal lupus and is found to have left bundle branch block, severely dilated cardiomyopathy with an ejection fraction of 25%, and a thin echogenic dyskinetic ventricular septum. The gene discussed is CALR; the disease is bundle branch block.