BACKGROUND/PURPOSE: Incontinentia pigmenti is a rare, X-linked, dominant genodermatosis affecting skin, teeth, eyes, and central nervous system. Symptoms are associated with mutations in the nuclear factor-kappa B essential modulator (NEMO) gene on chromosome Xq28. Here, a subpopulation of Chinese patients with incontinentia pigmenti were examined to investigate the frequency and pattern of NEMO mutations, and to analyze their clinical features. METHODS: From January 1996 to August 2006, 52 participants (21 probands and 31 family members) were screened for symptoms of incontinentia pigmenti and NEMO gene mutations. We designed a NEMO-specific PCR primer, referred to as In2S, to detect a deletion of exon 4-10 of the NEMO gene, which represents the mutation most frequently associated with incontinentia pigmenti. For participants without this deletion, all exons were sequenced to screen for other NEMO mutations. In addition, the clinical manifestations and family histories of the participants were analyzed. RESULTS: Exon 4-10 was deleted in 13 probands, and one proband had a novel point mutation (G549C) in exon 5 that converted a glutamine to a histidine. Seven probands (33%) had no mutation in any of the exons of the NEMO gene. One of four participants who presented with hyperpigmentation also had the exon 4-10 deletion. One patient had a positive family history before the study took place, but no NEMO mutation was identified in any of the family members. Remarkably, the mothers of three of the probands exhibited the exon 4-10 deletion; however, their clinical manifestations were subtle and unrecognizable. CONCLUSION: Mutational analysis of the NEMO gene was helpful in diagnosing incontinentia pigmenti among participants with a nearly normal phenotype or an incomplete form of the disease that only caused hyperpigmentation symptoms.