Detection of a known mutation M412T in the LDL receptor in a Chinese Thai FH family

Background: Familial hypercholesterolemia (FH) is an autosomal dominant hypercholesterolemia caused by mutation in the LDL receptor gene. M412T mutation of the LDL receptor gene was previously observed in a single female patient diagnosed as having primary hypercholesterolemia. However, the analysis was incomplete and there was no confirmation of the M412T as the FH-causing mutation. We identified a mutation in the LDL receptor gene that underlines the severe FH phenotype in a new case, a female Chinese Thai patient. Methods: Identification was made by PCR-SSCP, direct DNA sequencing and confirmed by allele specific amplification (ASA) originally designed for this current study. Results: The entire LDL receptor gene screening revealed the genetic alteration that also caused M412T mutation in this new index patient. ASA analysis confirmed the DNA sequence in this patient and further identified three family members as M412T carriers. Conclusions: The finding of this mutation in 2 apparently unrelated index patients and the co-segregation of M412T and FH phenotype in the family of the present index case should provide evidence and confirm that the M412T was likely to be a disease-causing mutation. Whether M412T is common either as a founder or recurrent mutation among FH Chinese Thai population is unknown at present and remains to be clarified.