We identified two families with SDH mutations in which a family member with a PA did not carry the germline SDHX mutation: family 6 with two SDHC mutation-positive siblings had PA and/or PGL, whereas a first cousin had an NFPA but no SDHC mutation; and family 7 in whom the parent and child both had SDHD mutation-positive PGL and another child had a microprolactinoma but no SDHD mutation (Supplemental Figure 1). Here, SDHD is linked to Microprolactinoma.