Long-range PCR demonstrated that this mutation is an in-frame tandem duplication of exon 3 which also involves duplication of introns 3 and 2. At the junction between intron 3 and intron 2 there is an inverted 141 bp duplication of a sequence found later in intron 2. The duplication of exon 3 results in a loss of function in the expressed protein due either to defective binding to its receptor or failure to activate the receptor once bound. (J:86436)