Dysfunctional ABCG2 Gene?

I'm homozygous for five uncommon mutations on the ABCG2 gene, one of which is the Q141K mutation (rs2231142) which was shown to be a loss of function mutation.  I'm not sure of the relevance of the other 4 mutations.

rs2231142 MAF = 0.1194
rs4148157 MAF = 0.1006
rs2054576 MAF = 0.0998
rs1481012 MAF = 0.1188
rs4148155 MAF = 0.1180

Thinking that the genotypes may have been miscalled, I looked on OpenSNP to see if the minor allele frequency in that database was similar to the dbSNP database.  Sure enough, they were close, indicating that the genotypes are probably correct.  So how did I end up being homozygous in so many uncommon mutations on the same gene?  Perhaps my parents come from populations where the minor allele is more common.  Native American father + British isles descent mother?  De novo (not inherited from parents) point mutations? Whatever the case is I identified one other person on OpenSNP so far that has the same homozygous cluster.  Luckily for them, they do not also have any of the more serious SLC2A9 mutations (rs16890979 and/or rs6449213).  I wonder if they have gout.