IMPORTANCE: Despite recessive inheritance, X-linked dystonia-parkinsonism (Lubag disease) has also been described in women presenting with a late-onset isolated parkinsonian syndrome. Interestingly, unlike in other populations, there is a slight female predominance in the prevalence of parkinsonism in the Philippines. OBSERVATIONS: In a Filipino woman with suspected Parkinson disease, we confirmed the presence of all changes specific for X-linked dystonia-parkinsonism in genomic DNA. Subsequently, we analyzed complementary DNA and evaluated the methylation status of the androgen receptor gene. Owing to extremely skewed (98%:2%) X-chromosome inactivation, the patient expressed almost solely the mutated allele in a disease-specific change, rendering her molecularly comparable with a hemizygously affected man. CONCLUSIONS AND RELEVANCE: Skewed X-chromosome inactivation is the likely cause of parkinsonism in this heterozygous mutation carrier. Because women carriers of the genetic changes specific for X-linked dystonia-parkinsonism are common in the Philippines, the epigenetic factor of nonrandom X-chromosome inactivation may contribute to the skewing of the sex prevalence of parkinsonism toward women in this country, warranting further investigation.