Case 1: Hyperpigmented swirly patches in a toddler

A previously healthy eight-month-old female Chinese infant presented with hyperpigmented swirly patches over the abdomen and legs for the past two months. Two weeks before her visit, the infant developed a vesicular eruption within the hyperpigmented streaks, which the mother photographed (Figure 1). This eruption coincided with a febrile upper respiratory tract infection. Vesicles in a linear distribution overlying hyperpigmented streaks Medical history revealed that the patient was born to nonconsanguineous parents following a normal pregnancy and delivery. At birth, she exhibited a vesicular eruption that resolved within the first few weeks of life. This was the family's first pregnancy, with no history of previous miscarriages. The patient was otherwise healthy, with no history of seizures, developmental delay, delayed dentition or nail abnormalities. No one in the family had similar findings. On examination, the patient appeared well. She had a normal neurological, respiratory, cardiac and abdominal examination. The cutaneous examination revealed multiple hyperpigmented patches over the abdomen and legs in a swirled pattern along Blashko's lines (Figure 2). There were no residual vesicles or other cutaneous changes, and no nail dystrophy. Hyperpigmented swirly patches following the lines of Blashcko on the trunk The hyperpigmented streaks, the recent vesicular eruption and photographs from birth confirmed the diagnosis. Photographs from birth demonstrated linear vesicles following the lines of Blashcko on day 1 of life (Figure 3). Incontinentia pigmenti (IP) is an uncommon X-linked dominant disorder caused by mutation of the NEMO/IKBKG gene, an upstream transcriptional activator that mediates cell growth and apoptosis (1). This condition is marked by skin dyspigmentation associated with anomalies of other ectodermal structures, the eyes and the central nervous system. It derives its name from the histological finding of pigment incontinence in the basal layer of the epidermis and superficial dermis. Linear vesicles following the lines of Blaschko on day 1 of life The characteristic skin findings in IP are defined by four stages: vesiculobullous; verrucous; hyperpigmented; and atrophic/hypopigmented. Stage 1 begins within the first two weeks of life and affects 90% of infants with IP. Lesions appear as erythematous vesicles along Blaschko's lines on the trunk and limbs. The vesicles resolve by approximately four months of age; however, recurrences beyond infancy have been reported and can be triggered by fever and viral illness, as observed in our patient. Stage 2 begins at two to six weeks of life and is marked by verrucous hyperkeratotic papules and plaques, predominantly occurring on the extremities, which resolve by six months of life. The hyperpigmented stage follows and presents with brown-gray whorls and streaks along Blaschko's lines. Stage 3 lesions gradually resolve by adolescence with the development of stage 4 lesions, which consist of hypopigmented atrophic patches devoid of adnexal structures. These stages do not always occur sequentially and not all of the stages may be observed. Other cutaneous features of IP include nail changes and vertex alopecia. In an infant who presents with vesiculobullous or hyperpigmented lesions, a wide range of differential diagnoses are possible. Vesiculobullous lesions in the neonate raise concern for neonatal herpes simplex, whereas multiple hyperpigmented lesions raise suspicion for segmental pigmentary mosaicism, urticarial pigmentosa or neurofibromatosis type 1. IP is associated with several extracutaneous anomalies that can cause significant morbidity. Approximately one-third of patients have ocular anomalies. Retinal findings include retinal vascular changes, retinal detachment and optic nerve atrophy – all of which could lead to blindness. Other ocular anomalies include microphthalmia, strabismus, nystagmus, cataracts, sclera pigment changes and conjunctivitis. Neurological issues occur in up to 30% of patients and most often present with neonatal ischemic stroke and/or seizures in early infancy (2). Dental and oral abnormalities occur in approximately 50% of patients. The majority of abnormalities are dental, including peg teeth, hypodontia and delayed dentition. Oral findings include cleft palate or high-arched palate. The diagnosis of IP can be guided by the following criteria and detection of the NEMO/IKBKG mutation: major criteria consist of typical IP skin stages distributed along Blaschko's lines; and supportive minor criteria include dental, ocular and central nervous system anomalies, alopecia, abnormal hair, abnormal nails, palate anomalies, nipple and breast anomalies, multiple male miscarriages or typical skin histological findings (1). Skin findings in IP are pronounced but benign, and are treated symptomatically. However, patients should undergo prompt referral to ophthalmology because early treatment of patients with retinal ischemic vasculopathy can reduce the risk of retinal detachment. Referrals should also be made to dentistry and neurology, if clinically indicated. Our patient was referred to paediatric dentistry and ophthalmology. As of her most recent follow-up at 15 months of age, she had normal dentition, normal developmental milestones and no evidence of retinal neovascularization. Vesiculobullous lesions in newborns have a wide-ranging differential; the linear distribution of lesions in IP differentiates it from disorders such as neonatal herpes simplex. Skin manifestations in IP are benign; the more concerning features are the associated extracutaneous findings including retinal vascular abnormalities, dental anomalies and potential neurological sequelae. In incontinentia pigmenti, stage 1 disease can recur with febrile illnesses past the infant period.

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