Case report The case regards a neonate of 20 days with cutaneous lesions characterized by linear plaques of vesicular or blister type on erythematous striae covering the trunk, limbs and groin, especially along Blaschko’s lines. The clinical findings suggested incontinentia pigmenti (IP) of type II (Bloch-Sulzberger disease). This diagnosis was confirmed by molecular genetic investigation revealing genomic deletion of exons 4–10 of the NEMO gene, which was not present in the parents and hence to be regarded as a new mutation. Type II IP is due to a defect of cutaneous pigmentation caused by a single dominant gene linked to the X chromosome (Xq28) with multisystemic involvement (neurological, skeletal and dental) in over 50% of cases. IP is the result of mutation of the NEMO/IKK-y gene codifying a critical component of the system activating the nuclear factor-κB (NF-κB). This is a rare disease (only 700 cases being described in the literature) found all over the world and primarily in females. In 90% of cases the disease manifests itself at birth with characteristic cutaneous lesions that can evolve in 4 stages, often in fixed chronological order (vesicular, warty, hyperpigmented, hypopigmented-atrophic). As was to be hoped, the patient presented a progression of cutaneous lesions from the vesicular stage to hyperpigmentation over a span of 4 months.
Conclusion The case appears to demonstrate perfectly the importance of clinical-pathological correlation in ensuring the correct diagnostic approach to a rare disease. Treatment of the cutaneous lesions is not usually required.