GDAP1 and bile duct papillary neoplasm: More recent studies have shown non-Mendelian inheritance, with concomitant MFN2 and GDAP1 variants resulting in disease.88 89 Importantly, other family members in the above cases harbouring a heterozygous variant in either GDAP1 or MFN2, were asymptomatic, presented with a subclinical phenotype, or had mild IPN.86, 89