 There are no common mutations that cause ALD, most are private or familial.Almost 600 different mutations have been identified, approximately half are missense mutations, one quarter are frameshifts, with in-frame deletions and splicing defects making up the remainder.The incidence of new mutations in ALD (those occurring spontaneously, rather than being inherited from a carrier parent) is estimated at approximately 4.1%, with the possibility that these are due to germline mosaicism.