Beyond the usual suspects: a case of incontinentia pigmenti diagnosed after exhaustive exclusion

Abstract

Incontinentia pigmenti (IP) is a rare X-linked dominant disorder caused by IKBKG gene mutations. Due to its rarity, early diagnosis is often delayed despite characteristic clinical features. A 12-day-old female born to healthy parents presented with an asymptomatic vesiculobullous rash following the lines of Blaschko. Present since birth, the tense blisters and bullae spread to the flexural extremities and genitalia, largely sparing the trunk. Hair, nails, and mucosa were unaffected. Tests revealed mild eosinophilia (12.6%), while comprehensive infectious screens were negative. A skin biopsy yielded nonspecific results, notably lacking melanin incontinence. Driven by strong clinical suspicion, genetic testing was performed. PCR amplification confirmed a common deletion within the IKBKG gene, successfully establishing the diagnosis. Managed with topical steroids and antibiotics, the lesions largely subsided by four months of age. This case underscores the importance of recognizing Blaschko-linear vesiculobullous lesions in neonates and highlights the critical role of genetic screening in confirming IP when the histopathology is inconclusive.