The group of epidermal nevus syndromes Part II. Less well defined phenotypes

Neuroimaging manifestations of epidermal nevus syndrome

Epidermal nevus syndrome (ENS) represents a diverse group of rare neurocutaneous diseases associated with the presence of characteristic epidermal nevi (EN) in the skin and extracutaneous manifestations in the eyes, skeletal, urogenital and central nervous systems. We present a case series of 7 children with ENS, with specific attention to the neuroradiological characteristics of this entity.

Hypertrichotic patches as a mosaic manifestation of Proteus syndrome

BACKGROUND

Proteus syndrome is an overgrowth disorder caused by a mosaic activating AKT1 variant. Hair abnormalities in Proteus syndrome have rarely been reported, and frequencies of such findings have not been elucidated.

OBJECTIVE

To define the types and frequencies of hair findings in individuals with Proteus syndrome.

METHODS

A cross-sectional study was conducted of individuals with clinical features of Proteus syndrome and a confirmed pathogenic variant in AKT1 evaluated between November 1996 and June 2019 at the National Institutes of Health Clinical Center. Medical records were reviewed for patterning, density, and color of hair on the body and scalp.

RESULTS

Of 45 individuals evaluated, 29 (64%) had asymmetric hypertrichosis on the body. This included unilateral blaschkoid hypertrichotic patches overlying normal skin or epidermal nevi in 16 (36%), unilateral nonblaschkoid hypertrichotic patches in 11 (24%), and unilateral limb hypertrichosis in 10 (22%). Diffuse, scattered, or patchy changes in scalp hair density or color were present in 11 individuals (24%).

LIMITATIONS

The retrospective, observational design, and limited longitudinal follow-up.

CONCLUSIONS

Asymmetric variations in hair distribution, thickness, length, and color contribute to the overall mosaic appearance of the skin in Proteus syndrome, an observation that provides novel insights into the role of phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) signaling in skin appendage development.

Multiple adenomatoid odontogenic tumors in a patient with Schimmelpenning syndrome

Schimmelpenning syndrome (SS) is a congenital neurocutaneous disorder characterized by the presence of linear nevus sebaceous, ophthalmic, neurologic, skeletal, urologic, and cardiovascular alterations. Oral manifestations related to SS mainly include dental defects, papillary lesions in the oral mucosa, giant cell lesions of the jaws, and odontogenic tumors. Here, we report the first case of multiple adenomatoid odontogenic tumor observed in a patient with SS.

Epidermal Nevi and Related Syndromes -- Part 1: Keratinocytic Nevi

Epidermal nevi are hamartomatous lesions derived from the epidermis and/or adnexal structures of the skin; they have traditionally been classified according to their morphology. New variants have been described in recent years and advances in genetics have contributed to better characterization of these lesions and an improved understanding of their relationship with certain extracutaneous manifestations. In the first part of this review article, we will look at nevi derived specifically from the epidermis and associated syndromes.

Epidermal nevus syndromes: New insights into whorls and swirls

Knowledge of the molecular underpinnings of many epidermal nevi and epidermal nevus syndrome has expanded rapidly in recent years. In this review and update on epidermal nevus syndrome, we will cover recent genetic discoveries involving epidermal nevi, including nevus sebaceus, keratinocytic epidermal nevus, nevus comedonicus, congenital hemidysplasia with ichthyosiform nevus and limb defects syndrome, phakomatosis pigmentokeratotica, Becker's nevus, porokeratotic adnexal ostial nevus, inflammatory linear verrucous epidermal nevi, and cutaneous-skeletal hypophosphatemia syndrome. We will discuss how newly defined mutations relate to the biology reflected in the cutaneous patterns seen in these mosaic disorders and how new molecular data has informed our understanding of these diseases and shaped management decisions.

Mosaic Disorders of the PI3K/PTEN/AKT/TSC/mTORC1 Signaling Pathway

Somatic mutations in genes of the PI3K/PTEN/AKT/TSC/mTORC1 signaling pathway cause segmental overgrowth, hamartomas, and malignant tumors. Mosaicism for activating mutations in AKT1 or PIK3CA cause Proteus syndrome and PIK3CA-Related Overgrowth Spectrum, respectively. Postzygotic mutations in PTEN or TSC1/TSC2 cause mosaic forms of PTEN hamartoma tumor syndrome or tuberous sclerosis complex, respectively. Distinct features observed in these mosaic conditions in part reflect differences in embryological timing or tissue type harboring the mutant cells. Deep sequencing of affected tissue is useful for diagnosis. Drugs targeting mTORC1 or other points along this signaling pathway are in clinical trials to treat these disorders.

Ocular manifestations of genetic skin disorders

Genetic skin diseases, or genodermatoses, often have extracutaneous manifestations. Ocular manifestations in particular can have significant clinical implications, like blindness. Other manifestations, such as the corneal opacities that occur in X-linked ichthyosis, are asymptomatic but characteristic of a particular genodermatosis. Ophthalmologic examination can aid in diagnosis when characteristic findings are seen. The genodermatoses with ocular manifestations will be reviewed, but neurocutaneous, syndromes, genetic pigmentary disorders, and genetic metabolic diseases are not included because they are covered elsewhere in this issue.

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.

Nevus Sebaceous and Its Association With Neurologic Involvement

Several terms are widely used to define cutaneous lesions affecting the epidermis in association with extracutaneous lesions. Recently, based on the wide spectrum of cutaneous epidermal lesions, the various underlying molecular mechanisms and patterns of associated features have led to improved definitions of these disorders. Nevus sebaceous syndrome has been placed under the umbrella term of epidermal nevus syndrome, in which the nevus sebaceous, a congenital hamartomatous lesion of the epidermis, is associated with anomalies involving the brain, eyes, and bones. Nevus sebaceous and neurologic manifestations were evaluated particularly based on their degree of intellectual delay, seizure type, treatment response, and electroencephalography and neuroradiological findings. A review of the literature in this topic is reported.

KRAS G12D mosaic mutation in a Chinese linear nevus sebaceous syndrome infant

BACKGROUND

Linear nevus sebaceous syndrome (LNSS) is a multisystem disorder that includes nevus sebaceous and central nervous system, ocular and skeletal anomalies. We report the first case of a KRAS G12D mosaic mutation in a patient diagnosed with LNSS.

CASE PRESENTATION

A 3-month-old female with a clinical diagnosis of LNSS presented with intermittent epilepsy. Her mother carefully collected a skin lesion sample from scratched-off scurf obtained from the patient's nails. DNA was extracted, and long-range PCR was performed to amplify the KRAS gene, which was then analyzed by next-generation sequencing. The results revealed the presence of a low-level heterozygous mutation in the KRAS gene (c.35C>T; p.G12D, 5 %).

CONCLUSIONS

These findings suggest that the KRAS somatic mosaic mutation in this patient may have caused her skin and eye lesions and epilepsy. With this correct diagnosis, the infant can be effectively treated.

Epidermal nevi with aberrant epidermal structure in keratinocytes and melanocytes

Epidermal nevi are congenital cutaneous hamartomas caused by embryonic somatic mutations. Ultrastructural features of adult epidermal nevi have rarely been investigated. Herein, we report a case involving a Japanese adult who had epidermal nevi with right congenital blindness and a right accessory nipple. The histopathologic and ultrastructural studies showed divergent abnormal epidermal structures in both melanocytes and keratinocytes. Our case indicates the need to further investigate histopathologic, ultrastructural, and genetic associations in adult epidermal nevi.

Epidermal nevus syndromes

The term epidermal nevus syndrome (ENS) has been used to describe the association of epidermal hamartomas and extracutaneous abnormalities. Although many continue to use the term "ENS," it is now understood that this is not one disease, but rather a heterogeneous group with distinct genetic profiles defined by a common cutaneous phenotype: the presence of epidermal and adnexal hamartomas that are associated with other organ system involvement. One commonality is that epidermal nevi often follow the lines of Blaschko and it appears the more widespread the cutaneous manifestations, the greater the risk for extracutaneous manifestations. The majority of the extracutaneous manifestations involve the brain, eye, and skeletal systems. The CNS involvement is wide ranging and involves both clinical manifestations such as intellectual disability and seizures, as well as structural anomalies. Several subsets of ENS with characteristic features have been delineated including the nevus sebaceus syndrome, Proteus syndrome, CHILD syndrome, Becker's nevus syndrome, nevus comedonicus syndrome, and phakomatosis pigmentokeratotica. Advances in molecular biology have revealed that the manifestations of ENS are due to genomic mosaicism. It is likely that the varied clinical manifestations of ENS are due in great part to the functional effects of specific genetic defects. Optimal management of the patient with ENS involves an interdisciplinary approach given the potential for multisystem involvement. Of note, epidermal nevi have been associated with both benign and malignant neoplasms, and thus ongoing clinical follow-up is required.

Photoletter to the editor: A neurocutaneous rarity: phacomatosis pigmentokeratotica

Phacomatosis pigmentokeratotica is characterized by the coexistence of nevus sebaceus, papular nevus spilus and associated neurologic abnormalities. We report a case of phacomatosis pigmentokeratotica in a 28-year-old male who presented with palmar-plantar dysesthesia and ipsilateral brain hemiatrophy. As a characteristic neuroimaging finding of the disorder, we found multiple hypointense lesions involving the ipsilateral hemisphere.

Garcia-Hafner-Happle syndrome: A case report and review of a rare sub-type of epidermal nevus syndrome

Garcia-Hafner-Happle syndrome, also known as Fibroblast growth factor receptor 3 epidermal nevus syndrome, is a new neurocutaneous phenotype, which has been identified in 2008 by Garcı'a-Vargas et al. The disorder is caused by a mosaic R248C mutation of the FGFR3 gene, which is characterized by a keratinocytic epidermal nevus, acanthosis nigricans, and neurological abnormalities like seizures, intellectual impairment, cortical atrophy, and underdevelopment of corpus callosum. The epidermal nevus syndromes represent a group of distinct disorders in which an epidermal nevus is associated with abnormalities in other organ systems like central nervous system, cardiovascular system, genitourinary system, eyes, and bone. Recently, nine well-defined different epidermal nevus syndromes (ENSs) have been identified on clinical, histopathologic, and molecular basis. We present here the details of a patient with the clinical features and skin biopsy findings suggestive of Garcia-Hafner-Happle syndrome.

Late onset epidermal nevus with hypertrichosis and facial hemihypertrophy

Epidermal nevus syndromes are rare conditions, characterized by different types of keratinocytic or organoid epidermal nevi in association with ocular, neurological, and skeletal manifestations. We present a case of late onset epidermal nevus with hypertrichosis and hemihypertrophy of face. Genetic analysis did not reveal presence of FGFR3 or PIK3CA mutations. The patient has features that cannot be categorized into the present well-known syndromes.

Therapeutic effects of CO2 laser therapy of linear nevus sebaceous in the course of the Schimmelpenning-Feuerstein-Mims syndrome

The Schimmelpenning-Feuerstein-Mims (SFM) syndrome is a rare phakomatosis which comprises a nevus sebaceous of Jadassohn, seizures and developmental delay associated with a wide spectrum of extracutaneous abnormalities including neurological, skeletal, ocular, cardiovascular and urogenital defects. We are presenting a case of an 18-year-old patient with systemic features of the SFM syndrome and an extensive linear nevus sebaceous partially removed with a carbon dioxide (CO2) laser. The treatment options of skin lesions in patients with SFM are discussed.

Epidermal nevus and ameloblastoma: a rare association

Epidermal nevi are clinical manifestations of a malformation affecting the embryonic ectoderm. They appear as linear verrucous lesions and are more often located in the skin of the trunk or the extremities. Rarely, verrucous lesions affect the oral mucosa. Epidermal nevi can be a component of epidermal nevus syndrome (ENS), which is characterized by malformations involving several organs, such as the central nervous system. ENS is rarely associated with other solid tumors. We present the case of a patient affected by ENS who developed maxillary and mandibular ameloblastomas. Epidermal nevi were located in the left middle and lower third of the face and in the left cervical region, whereas the ameloblastomas arose within the left maxillary mucosa and within the left mandibular ramus. Features of the syndrome are described and the relevant literature is reviewed.

Papular epidermal nevus with "skyline" basal cell layer (PENS) with extracutaneous findings

Papular epidermal nevus with "skyline" basal cell layer (PENS), a variant of epidermal nevus, was recently described in otherwise normal children. We describe herein a patient with multiple, typical PENS lesions associated with peculiar facies, bilateral Achilles tendon shortening, and mild psychomotor delay. The association of PENS with extracutaneous manifestations suggests the possibility of a new type of epidermal nevus syndrome, for which we propose the term PENS syndrome.

Superimposed linear psoriasis: a historical case revisited

In 1978, a case of "ichthyosis vulgaris and ILVEN syndrome (inflammatory linear verrucous epidermal nevus)" was presented by Johannes Ring, of Munich [1]. Based on present knowledge, a diagnosis of superimposed linear psoriasis appears simpler and more appropriate because the 10-year-old girl also had multiple psoriatic plaques, with a symmetrical and non-segmental distribution. The linear manifestation most likely reflects the clonal outgrowth of a population of cells harboring a postzygotic mutation that increased the predisposition to psoriasis.