Maternal autoimmune disease accounts for 60-90% of congenital complete heart block (CCHB) cases presenting in utero or in the neonatal period.[1], [2], [3] Transplacentally transferred maternal autoantibodies anti-Ro/SSA and/or anti-La/SSB bind fetal cardiac conduction cells, producing an inflammatory response with lymphocytic infiltration and resulting in fibrosis and calcification, the basis for congenital AV block.[4], [5], [6], [7] Multiple theories have been proposed for the pathogenesis of CCHB centering on calcium homeostasis. In the ‘apoptosis hypothesis,’ Ro52 antibodies dysregulate calcium homeostasis and induce apoptosis in cardiomyocytes. La autoantibodies then bind apoptotic cells and instigate opsonization in genetically pre-disposed fetuses.[8], [9], [10], [11] In the ‘cross-reactivity hypothesis,’ cross-reactivity between maternal autoantibodies Anti-Ro/La and calcium channel subunits leads to impaired electric signaling. [11]

Histologically, maternal antibody induced CCHB presents primarily as AV nodal fibrosis with other findings including fibrosis and calcification of the sinoatrial (SA) node and bundle of His, endocardial fibroelastosis, papillary muscle fibrosis, valvular disease, chordal rupture, calcification of the atrial septum, fetal cardiomyopathy, and mononuclear pancarditis.[1], [2], [3], [4], [5], [6] Severe valvular disease is more common in third-trimester fetal demise compared to second-trimester fetal demise and post-natal deaths.[6] Given the wide variety of histologic pathology findings and dearth of existing reports discussing them, we report the full autopsy and clinical information for a unique case of calcification in both atrial approaches to the AV node, the AV node itself, and proximal left and right bundle branches associated with maternal anti-SSA/Ro in the presence of neonatal high degree AV block.