Incontinentia pigmenti versus hypomelanosis of Ito: the whys and wherefores of a confusing issue

Hypomelanosis of Ito with Multiple Congenital Anomalies

Hypomelanosis of Ito (HI) is a neurocutaneous disorder, also known as incontinentia pigmenti achromians. HI has been associated with chromosomal abnormalities, especially mosaicism. Herein, we report a case of HI with multiple congenital anomalies. A 2-month-old girl presented with multiple linear and whorling hypopigmentation on the face, trunk, and both extremities and patch alopecia on the scalp. Moreover, she had conical teeth, aniridia of the both eyes, and multiple musculoskeletal problems, including syndactyly and coccyx deviation. Cytogenetic analysis on peripheral blood was normal 46, XX, and no mutation was found in IKBKG gene test.

Total Hemi-overgrowth in Pigmentary Mosaicism of the (Hypomelanosis of) Ito Type: Eight Case Reports

Pigmentary mosaicism of the (hypomelanosis of) Ito type is an umbrella term, which includes phenotypes characterized by mosaic hypopigmentation in the form of streaks, whorls, patchy, or more bizarre skin configurations (running along the lines of Blaschko): these cutaneous patterns can manifest as an isolated skin disorder (pigmentary mosaicism of the Ito type) or as a complex malformation syndrome in association with extracutaneous anomalies (most often of the musculoskeletal and/or nervous systems) (hypomelanosis of Ito). Affected individuals are anecdotally reported to have also partial or total body hemi-overgrowth (HOG), which often causes moderate to severe complications.We studied the occurrence and features of HOG in the 114 children and adults with mosaic pigmentary disorders of the Ito type diagnosed and followed up (from 2 to 22 years; average follow-up 16 years) at our Institutions.Eight patients (5 M, 3 F; aged 4 to 25 years; median age 16 years) out of the 114 analyzed (7%) fulfilled the criteria for unilateral HOG, with differences in diameter ranging from 0.4 to 4.0 cm (upper limbs) and 1.0 to 9.0 cm (lower limbs). Moreover, among these 8 patients, 5/8 filled in the 75th to 90th percentile for height; 6/8 had associated kyphoscoliosis; and 5/8 showed cognitive delays. No tumour complications were recorded. Overall, 6/8 HOG patients presented with additional (extracutaneous) syndromic manifestations, apart from the HOG (ie, with a clinical phenotype of hypomelanosis of Ito).The present study, which includes children and adults with the longest follow-up so far recorded, confirms the association between pigmentary mosaicism of the Ito type and HOG lowering previous estimates (7% vs 16%) for HOG in the context of mosaic hypopigmentation. A careful examination, looking at subtle to moderate asymmetries and associated complications within the spectrum of these mosaic pigmentary disorders, is recommended.

Mosaic Neurocutaneous Disorders and Their Causes

Neurocutaneous disorders are a heterogeneous group of conditions (mainly) affecting the skin [with pigmentary/vascular abnormalities and/or cutaneous tumours] and the central and peripheral nervous system [with congenital abnormalities and/or tumours]. In a number of such disorders, the skin abnormalities can assume a mosaic patterning (usually arranged in archetypical patterns). Alternating segments of affected and unaffected skin or segmentally arranged patterns of abnormal skin often mirror similar phenomena occurring in extra-cutaneous organs/tissues [eg, eye, bone, heart/vessels, lung, kidney and gut]. In some neurocutaneous syndromes the abnormal mosaic patterning involve mainly the skin and the nervous system configuring a (true) mosaic neurocutaneous disorder; or an ordinary trait of a neurocutaneous disorder is sometimes superimposed by a pronounced linear or otherwise segmental involvement; or, lastly, a neurocutaneous disorder can occur solely in a mosaic pattern. Recently, the molecular genetic and cellular bases of an increasing number of neurocutaneous disorders have been unravelled, shedding light on the interplays between common intra- and extra-neuronal signalling pathways encompassing receptor-protein and protein-to-protein cascades (eg, RAS, MAPK, mTOR, PI3K/AKT and GNAQ pathways), which are often responsible of the mosaic distribution of cutaneous and extra-cutaneous features. In this article we will focus on the well known, and less defined mosaic neurocutaneous phenotypes and their related molecular/genetic bases, including the mosaic neurofibromatoses and their related forms (ie, spinal neurofibromatosis and schwannomatosis); Legius syndrome; segmental arrangements in tuberous sclerosis; Sturge-Weber and Klippel-Trenaunay syndromes; microcephaly/megalencephaly-capillary malformation; blue rubber bleb nevus syndrome; Wyburn-Mason syndrome; mixed vascular nevus syndrome; PHACE syndrome; Incontinentia pigmenti; pigmentary mosaicism of the Ito type; neurocutaneous melanosis; cutis tricolor; speckled lentiginous syndrome; epidermal nevus syndromes; Becker's nevus syndrome; phacomatosis pigmentovascularis and pigmentokeratotica; Proteus syndrome; and encephalocraniocutaneous lipomatosis.

Hypomelanosis of Ito: a round on the frequency and type of epileptic complications

There is an ample evidence that hypopigmentation of the skin along the Blaschko's lines is frequently associated with neurological disorders. Nowadays, the term "Hypomelanosis of Ito" (HI) is applied when, together with the cutaneous lesions, various and multisystem organs are involved. Among these, the most frequent are cerebral manifestations, such as cognitive delay and epileptic seizures. For this reason, hypomelanosis of Ito has been included in the group of neurocutaneous syndromes, neurologic manifestations being one of the most frequent. Epileptic seizures have been reported in patients with this disorder, but in a very few particular attention has been focused on the type and frequency of epilepsy and on the response to the treatment. Herein, we report on five patients with HI who showed episodes of epileptic seizures with onset in childhood, in absence of malformative anomalies except for the skin lesions. A survey on the frequency and types of epileptic seizures in HI children and in the literature is reported.

Incontinentia pigmenti and hypomelanosis of Ito

Incontinentia pigmenti (IP) is a rare X-linked dominant neurocutaneous disorder affecting ectodermal tissue: skin, eyes, central nervous system, hair, nails, and teeth. It is usually lethal for males in utero. The involved gene is NEMO, an essential component of the nuclear factor-kappa B (NF-κB) signaling pathway. Skin lesions are highly diagnostic, occurring in neonates, with a particular distribution on Blaschko lines. The severity of the disease is related to ocular and neurological impairment. The hallmark of ocular IP is retinal vasculopathy including peripheral retinal vascular nonperfusion, macular infarction and neovascularization, and preretinal neovascularization. CNS involvement consists of seizures, mental retardation, hemiparesis, spasticity, microcephaly, cerebellar ataxia, and coma. It often occurs in neonates. Some patients have persistent pharmacoresistant seizures throughout life. MRI findings consist essentially in: white-matter lesions; scattered cortical neuronal necrosis; multiple cerebral infarctions; cerebral atrophy, hypoplasia of the corpus callosum, encephalomalacia and neuronal heterotopia. A predominant role of vascular occlusive phenomena in small vessels is highly suspected. In fact several intricate mechanisms could be discussed: vascular, inflammatory, developmental mechanisms. Their role and predictive factors of IP CNS involvement in neonatal IP need to be better understood to identify effective innovative therapies. Hypomelanosis of Ito can occur in the neonate, infancy, or childhood, be isolated or diffuse, often following the Blaschko lines, and can fade in childhood or adulthood. It is due to reduced melanin in the epidermis. Eye, central nervous (mental retardation, epilepsy, language disabilities, motor system dysfunction, psychiatric symptoms including autism - with frequent cortical malformations including hemimegalencephaly and white matter involvement), and musculoskeletal systems can also be affected. Mosaicism with various chromosomal rearrangements has been reported.

Pigmentary mosaicism, subcortical band heterotopia, and brain cystic lesions

A 10-year-old boy presented with a severe and diffuse mosaic skin hypopigmentation running (in narrow bands) along the lines of Blaschko associated with mosaic areas of alopecia, facial dysmorphism with midface hypoplasia, bilateral punctate cataract, microretrognathia, short neck, pectus excavatum, joint hypermobility, mild muscular hypotonia, generalized seizures, and mild mental retardation. Cranial magnetic resonance imaging revealed hypoplastic corpus callosum (primarily posterior), subcortical band heterotopia, and diffuse subcortical, periventricular cystic-like lesions. Similar dysmorphic features were observed in the child's mother, but with no imaging abnormalities. The facial phenotype coupled with the cysts in the brain was strongly reminiscent of the oculocerebrorenal Lowe syndrome. Full chromosome studies in the parents and the proband and mutation analysis on peripheral blood lymphocytes (and on skin cultured fibroblasts from affected and unaffected skin areas in the child) in the genes for subcortical band heterotopia (DCX (Xq22.3-q23)], lissencephaly (PAFAH1B1, alias LIS1, at 17p13.3), and oculocerebrorenal syndrome of Lowe (OCRL at Xq23-q24)] were unrevealing. This constellation of multiple congenital anomalies including skin hypopigmentation and eye, musculoskeletal, and nervous system abnormalities was sufficiently characterized to be regarded as a novel example of pigmentary mosaicism of the Ito type (i.e., hypomelanosis of Ito).

Pigmentary mosaicism following the lines of Blaschko in a girl with a double aneuploidy mosaicism: (47,XX,+7/45,X)

We report on a 6-year-old girl with linear streaks of apparent hypopigmentation and hyperpigmentation following the Blaschko lines, growth retardation, bupthalmos of the left eye, and mild mental retardation. She had a 45,X karyotype in lymphocytes. In cultured fibroblasts a double aneuploidy mosaicism was detected, consisting of a cell line with trisomy for chromosome 7 and a cell line with monosomy for the X-chromosome and no cell line with a normal karyotype. Cutis tricolor or three levels of pigmentation in different skin areas suggested presence of a third, probably normal cell line. Double aneuploidy mosaicism of a cell line with monosomy X and a cell line with trisomy of an autosome is a rare finding. The combination of monosomy X with trisomy of chromosomes 8, 10, 13, 18, and 21 has been reported, but not the combination with trisomy 7. In the 45,X cell line, microsatellite analysis showed loss of the maternal X-chromosome, and presence of a maternal and paternal chromosome 7. The 47,XX,+7 cell line showed a paternal and a maternal X-chromosome, and a paternal and two identical maternal chromosomes 7. Mechanisms that might explain this double aneuploidy mosaicism are discussed.

Incontinentia pigmenti: a window to the role of NF-kappaB function

Incontinentia pigmenti is an uncommon X-linked dominant genodermatosis primarily affecting females. Its hallmark is a unique skin eruption that presents in infancy along the lines of Blaschko and evolves through four stages: inflammatory, verrucous, hyperpigmented, and atrophic. Other persistent findings of the disease include alopecia and dental anomalies. In a minority of cases, serious ophthalmologic and neurological alterations may occur. Mutations in the NF-kappaB essential modulator (NEMO) that lead to an inability to activate the NF-kappaB pathway produce IP. Less deleterious mutations in NF-kappaB essential modulator give rise to hypohidrotic ectodermal dysplasia with immune deficiency in affected males, a related but distinct phenotype. These recent discoveries provide insight into the crucial role of NF-kappaB function in regulating the developmental, inflammatory, immune, and anti-apoptotic responses of the skin and other organs.

Surviving male with incontinentia pigmenti: a case report

Incontinentia pigmenti, or Block-Sulzberger Syndrome, is an X-linked dominant disorder with characteristic skin, hair, eye and tooth abnormalities. It is classically considered a male-lethal disorder with recurrent miscarriages of male foetuses. A few cases of surviving males with incontinentia pigmenti have been reported in the medical literature. This article reports the medical and dental findings of a boy diagnosed with incontinentia pigmenti.

Pigmentary mosaicism of the hyperpigmented type in two half-brothers

Pigmentary mosaicism is a heterogeneous cutaneous phenotype that is often associated with extracutaneous anomalies. It is widely accepted that these phenotypes arise de novo as a result of a postzygotic mutation, leading to a mosaic status of the embryo. In the vast majority of cases, the occurrence of pigmentary mosaicism is sporadic. We report two paternal half-brothers affected with pigmentary mosaicism of the hyperpigmented type. The hyperpigmentation in both patients is distributed along the lines of Blaschko. In addition, mental retardation, facial asymmetry, short stature, scoliosis, and short fingers with clinodactyly of the 5th digit were noted in one of them. Chromosome analysis in this 15-year-old patient demonstrated a mosaic 46,XY,dup(3)(p21.3;pter)/46,XY with 12% aberrant cells in lymphocytes and 2% in skin fibroblasts derived from a hyperpigmented area. His nine-year-old half-brother had similar systematized hyperpigmented skin lesions, macrocephaly, facial asymmetry, and clinodactyly of the 5th digit. Chromosome analysis of peripheral lymphocytes showed a normal karyotype 46,XY. A skin biopsy could not be obtained. So far, some familial cases of hypopigmentation along the lines of Blaschko have been reported, but familial occurrence of the hyperpigmented type of pigmentary mosaicism appears to be extremely unusual. It is difficult to establish a causal relationship with the chromosomal mosaicism as observed in patient 1. Paradominant transmission seems unlikely because this would likewise imply that the chromosomal mosaicism is an incidental finding.