Focal dermal hypoplasia (FDH) is an X-linked dominant disorder characterized by patchy dermal hypoplasia with digital, ocular and dental abnormalities. Very recently, mutations in the PORCN gene were demonstrated to cause FDH. Here, we described three unrelated Thai girls who were sporadic cases of FDH. One of them had unilateral athelia, which has never been described in FDH. Mutation analysis by polymerase chain reaction sequencing the entire coding regions of PORCN successfully revealed three potentially pathogenic mutations, c.373+1G>A, c.737_738insA and c.1094G>A (p.R365Q). One was found in each of three patients. In addition, another sequence variant c.682C>T (p.R228C) with an inconclusive role was found in one patient and her unaffected mother. The two missense mutations were not detected in at least 100 ethnic-matched control chromosomes, and all four mutations had never been previously described. X chromosome inactivation studies showed random patterns in all of them. This study demonstrates that PORCN is the gene responsible for FDH across different populations and extends the total number of confirmed mutations to 26.