Dejerine-Sottas syndrome (DSS), a severe demyelinating peripheral neuropathy with onset in infancy, has been associated with mutations in either PMP22 or MPZ. Most cases of DSS are caused by a single heterozygous dominant point mutation. We identified three de novo point mutations in MPZ exon 3 in a sporadic DSS patient. These three point mutations occur on the same allele and result in three novel amino acid substitutions: Ile(85)Thr, Asn(87)His, and Asp(99)Asn. Our data raise the question as to the potential mechanism(s) involved in the formation of multiple point mutations at a given locus.