Epidermal nevus syndromes: New insights into whorls and swirls

Widespread keratinocytic epidermal nevus with an associated chylous pericardial effusion

A 17-year-old male presented for review of a widespread keratinocytic epidermal nevus (KEN) in the setting of a chronic pericardial effusion. Biopsy of the epidermal nevus revealed a KRAS mutation. Pericardiocentesis revealed a chylous effusion and magnetic resonance lymphangiogram demonstrated an underlying lymphatic malformation. There are rare case reports of KEN with an associated KRAS mutation. This case highlights the importance of being alert to epidermal nevus syndrome, particularly in patients with a widespread nevus and seemingly unrelated pathology.

Reversibility and developmental neuropathology of linear nevus sebaceous syndrome caused by dysregulation of the RAS pathway

Linear nevus sebaceous syndrome (LNSS) is a neurocutaneous disorder caused by somatic gain-of-function mutations in KRAS or HRAS. LNSS brains have neurodevelopmental defects, including cerebral defects and epilepsy; however, its pathological mechanism and potentials for treatment are largely unclear. We show that introduction of KRAS^G12V in the developing mouse cortex results in subcortical nodular heterotopia and enhanced excitability, recapitulating major pathological manifestations of LNSS. Moreover, we show that decreased firing frequency of inhibitory neurons without KRAS^G12V expression leads to disrupted excitation and inhibition balance. Transcriptional profiling after destabilization domain-mediated clearance of KRAS^G12V in human neural progenitors and differentiating neurons identifies reversible functional networks underlying LNSS. Neurons expressing KRAS^G12V show molecular changes associated with delayed neuronal maturation, most of which are restored by KRAS^G12V clearance. These findings provide insights into the molecular networks underlying the reversibility of some of the neuropathologies observed in LNSS caused by dysregulation of the RAS pathway.

The efficacy and safety of burosumab in two patients with cutaneous skeletal hypophosphatemia syndrome

Cutaneous skeletal hypophosphatemia syndrome (CSHS) is an ultra-rare mosaic disorder manifesting as skeletal dysplasia and FGF23-mediated hypophosphatemia, with some experiencing extra-osseous/extra-cutaneous manifestations, including both benign and malignant neoplasms. Like other disorders of FGF23-mediated hypophosphatemia including X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO), patients with CSHS have low serum phosphorus and active 1,25-dihydroxyvitamin D levels. Current treatment options for patients with CSHS include multiple daily doses of oral phosphorus and one or more daily doses of active vitamin D analog to correct the deficits. Recently, the fully human monoclonal antibody against FGF23 burosumab received US approval for the treatment of XLH and TIO, two rare diseases characterized by FGF23-mediated hypophosphatemia leading to rickets and osteomalacia. Given the similarities between the pathobiologies of these disorders and CSHS, we investigated the impact of burosumab on two patients, one pediatric and one adult, with CSHS who participated in separate, but similarly designed trials. In both the pediatric and adult patients, burosumab therapy was well-tolerated and contributed to clinically meaningful improvements in disease outcomes including normalization of phosphorus metabolism and markers of bone health, and improvements in skeletal abnormalities, fractures, and physical function. Reported adverse events were minimal, with only mild injection site reactions attributed to burosumab therapy. Together, these findings suggest that burosumab therapy is a promising therapeutic option for patients with CSHS.

A case of multiple, bilateral Becker's Nevi of the trunk and lower extremities in a young girl: A case report

A Becker's nevus typically appears as a single unilateral, well-demarcated, hyperpigmented patch over the upper trunk during adolescence. It uncommonly presents as multiple and bilateral patches and rarely involves a lower extremity. We describe the unusual case of a child with multiple, bilateral Becker's nevi of the trunk and lower extremities present since birth.

Nevus Sebaceus Arising Within a Scalp Whorl of a Healthy Male Neonate

Nevus sebaceus (NS) and scalp whorl are both benign congenital findings that have not previously been reported to occur simultaneously. In most cases, the isolated finding of a single, classic-appearing NS or a single hair whorl can be followed clinically with observation. However, the number of lesions, distribution, and size of NS along with atypical placement of a scalp hair whorl can indicate an underlying syndrome or even underlying cranial abnormalities. We present a unique case of NS arising within a hair whorl on the vertex scalp of an otherwise healthy male neonate. After ultrasound showed no vascular malformations or proliferations and no cranial extension at the site, the lesion was later treated with surgical excision at six months old per the parents' preference, thus allowing for histologic confirmation of NS. Additionally, we discuss herein the diagnostic implications, recommendations for work-up, and treatment options of NS.

The first case of Chinese phacomatosis pigmentokeratotica diagnosed by a missense HRAS mosaicism

Phacomatosis pigmentokeratotica (PPK) is a rare epidermal nevus (EN) syndrome, featured by co-occurrence of speckled lentiginous nevus (SLN) and nevus sebaceous (NS). The underlying mechanism has not been clarified. Pathogenic mutations in HRAS, KRAS and BRAF gene are recently recognized as the genetic cause of PPK. Here we present a case of Chinese PPK with a mosaic mutation in HRAS gene. Physical examination of the 4-year-old male proband showed NS locating on the scalp, with EN and SLN on trunk and extremities. Except congenital fundus vascular tortuosity, no evidence of extracutaneous abnormalities was found in this case. A rare heterozygous missense c. 181 C>A mosaic mutation in HRAS was identified in samples from NS, EN and pigmented nevus using next-generation sequencing and Sanger sequencing. Meanwhile, no mutation was found in the non-lesion skin, hair follicle, or blood DNA. Recent breakthrough in clinical manifestation, genetic mutation and prognosis of PPK is also reviewed.

Identification of Codon 146 KRAS Variants in Isolated Epidermal Nevus and Multiple Lesions in Oculoectodermal Syndrome: Confirmation of the Phenotypic Continuum of Mosaic RASopathies

Mosaic RASopathies are a molecularly heterogeneous group of (neuro)cutaneous syndromes with high phenotypical variability. Postzygotic variants in KRAS have been described in oculoectodermal syndrome (OES), encephalocraniocutaneous lipomatosis (ECCL) and epidermal nevus syndrome (ENS). This study confirms the continuum of mosaic neurocutaneous RASopathies showing codon 146 KRAS variants in an individual with OES and, for the first time, in an individual with (isolated) epidermal nevus. The presence of a nevus psiloliparus in individuals with OES indicates that this finding is not specific for ECCL and highlights the phenotypical overlap between ECCL and OES. The presence of the somatic KRAS variant in the nevus psiloliparus resolves the underlying molecular etiology of this fatty-tissue nevus. In addition, this finding refutes the theory of non-allelic twin-spotting as an underlying hypothesis to explain the concurrent presence of two different mosaicisms in one individual. The identification of codon 146 KRAS variants in isolated epidermal nevus introduces a new hot spot for this condition, which is useful for increasing molecular genetic testing using targeted gene sequencing panels.

[Benign skin neoplasms in children]

There are many different types of skin neoplasms in children and most are benign. Dermatologists should be able to differentiate between the various types of benign skin neoplasms and be able to recommend optimal treatment to concerned patients. Surgical removal of benign skin neoplasms is often the only treatment option. The aim of this paper is to provide a general overview of epidermal lesions (e.g., inflammatory linear verrucous epidermal nevus [ILVEN], nevus sebaceous), tumors of the epidermal appendages (e.g. pilomatrixoma), cutaneous neoplasms (e.g. angiofibroma), fibromatoses (e.g., knuckle pads), tumors comprised of fat, muscle, or bone tissue (e.g., osteoma cutis, subungual exostosis), epidermal cysts and pseudocysts, and pathologic fibrosis reactions after dermal injury (keloid). Scientific data are scarce and only in the last decade has it been possible to perform histopathological examinations and genetic studies together with detailed phenotyping to gain new understanding of the pathogenetic mechanisms.

Epidermal Nevi: What Is New

This article reviews the clinical findings of epidermal nevi and their associated syndromes and provides an update on their pathogenic genetic changes as well as targeted therapies detailed to date.

Scalp Nodules and Facial Droop in an Infant

A previously healthy, term, 5-week-old girl initially presented to her primary care physician with a solitary, enlarging scalp nodule. The infant was otherwise well without additional signs or symptoms of illness. Over the next several weeks, the nodule continued to grow, and additional lesions appeared on her scalp. An ultrasound of the primary nodule revealed a hypoechoic structure favored to represent a serosanguinous fluid collection. After evaluation by general surgery and dermatology, she underwent a scalp biopsy of the largest lesion. While biopsy specimen results were pending, her parents noted that she was developing increased irritability, difficulty closing her right eye, and facial weakness. She was referred to the emergency department where a right-sided facial droop involving the brow and forehead was noted. The skin biopsy specimen results, along with subsequent laboratory studies and imaging, led to the final diagnosis.

Congenital Pigmentary Anomalies in the Newborn

Congenital pigmentary anomalies may be evident at birth or soon after, with some birthmarks becoming apparent later in infancy or early childhood. It is important to recognize various pigmentary anomalies in the neonate, most of which are benign but a subset of which are associated with cutaneous morbidity or systemic ramifications and require further evaluation. This review will focus on pigmentary mosaicism, congenital melanocytic nevi, nevus spilus, dermal melanocytosis, and pigmentary anomalies associated with neurofibromatosis type 1 (café au lait spots, freckling, plexiform neurofibromas, nevus anemicus), tuberous sclerosis (hypomelanotic macules), and incontinentia pigmenti.

The Role of KRAS Mutations in Cortical Malformation and Epilepsy Surgery: A Novel Report of Nevus Sebaceous Syndrome and Review of the Literature

The rare nevus sebaceous (NS) syndrome (NSS) includes cortical malformations and drug-resistant epilepsy. Somatic RAS-pathway genetic variants are pathogenetic in NS, but not yet described within the brain of patients with NSS. We report on a 5-year-old boy with mild psychomotor delay. A brown-yellow linear skin lesion suggestive of NS in the left temporo-occipital area was evident at birth. Epileptic spasms presented at aged six months. EEG showed continuous left temporo-occipital epileptiform abnormalities. Brain MRI revealed a similarly located diffuse cortical malformation with temporal pole volume reduction and a small hippocampus. We performed a left temporo-occipital resection with histopathological diagnosis of focal cortical dysplasia type Ia in the occipital region and hippocampal sclerosis type 1. Three years after surgery, he is seizure-and drug-free (Engel class Ia) and showed cognitive improvement. Genetic examination of brain and skin specimens revealed the c.35G > T (p.Gly12Val) KRAS somatic missense mutation. Literature review suggests epilepsy surgery in patients with NSS is highly efficacious, with 73% probability of seizure freedom. The few histological analyses reported evidenced disorganized cortex, occasionally with cytomegalic neurons. This is the first reported association of a KRAS genetic variant with cortical malformations associated with epilepsy, and suggests a possible genetic substrate for hippocampal sclerosis.

A giant epidermal nevus of the face treated with a CO2 and dye laser combination: a case report and literature review

Epidermal nevi (EN) are cutaneous hamartomas present at birth, usually occurs in the trunk, the face, or the limbs, appearing as a patch of overgrowing skin. They may be small and localized, but they may interest extensive areas of the body. A 20 years old man came to our attention for an EN interesting all the face. The treatment protocol consisted of a session of CO₂ laser in order to vaporize thicker areas, followed by a session of dye laser on the area to prevent scarring. This treatment was performed under local anesthesia and sedation in three surgical sessions spaced 3 months from each other. Two sessions of dye laser spaced apart 6 months were performed during follow-up to further improve the esthetic outcome. The patient was followed for 2 years with no recurrence. Although surgery is still considered the gold standard in EN management, it is not always feasible. This novel combination technique can obtain optimal cosmetic results with no relapse within the period of follow up. Although further trials on a more significant number of patients are required, the combination of CO₂ and dye laser promises to become a valid therapeutic alternative when treating giant EN of the face.

Bilateral Systematised Epidermolytic Epidermal Nevus: A case report

Verrucous epidermal nevi (VEN) are benign congenital hamartomas consisting of keratinocytes. Histological examination mostly exhibits hyperkeratosis, acanthosis, papillomatosis and, rarely, the features of epidermolytic hyperkeratosis (EHK). We report a case of a 6-year-old boy who presented at Aga Khan University Hospital, Karachi, Pakistan with bilaterally symmetrical linear epidermal nevi following Blaschko’s lines and showing epidermolytic hyperkeratosis on histology. The patient was treated with topical keratolytics and emolients which led to considerable improvement. To the best of the authors’ knowledge, this is the first report of VEN from Pakistan.

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.

Association of Central Precocious Puberty with a Rare Presentation of Schimmelpenning-Feuerstein-Mims Syndrome in a Peruvian Girl

Schimmelpenning–Feuerstein–Mims syndrome (SFM), an epidermal nevus syndrome characterized by skin lesions, has an estimated incidence of 1 per 10 000 live births. Nevus sebaceous, the most common cutaneous lesion, and verrucous nevus, the less frequent lesion, are coupled with a wide range of extracutaneous manifestations. As part of these manifestations, rarely, central precocious puberty can arise. We report the case of a 1-year-5-month-old girl who presented to the Endocrinology and Metabolism Department with breast enlargement that began at one year of age, growth of pubic and axillary hair three months later, and vaginal bleeding that occurred five months later. During clinical examination, melanocytic nevi, with a diameter ranging from 3 to 5 mm, were noted on the face. Verrucous nevi of variable size with a tendency for coalescence following the lines of Blaschko and melanocytic nevi with a diameter ranging from 3 to 6 mm were observed on the right hemibody and on the left hemibody, respectively. Right asymmetry of the lower extremities was observed. Laboratory findings showed a significant increase in the levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) after the gonadotropin-releasing hormone (GnRH) stimulation test; additionally, imaging demonstrated advanced bone age and pubertal changes in the internal genitals. Analyses of the H-RAS, K-RAS, and N-RAS genes in the blood and in the skin were performed, and a missense mutation in exon 2 of the gene, H-RAS c37G > C (p.G13R), was detected in the latter. Treatment with triptorelin, a GnRH analog, was initiated, and it gave good clinical response. Epidermal nevus syndrome has a wide and variable systemic involvement. Thus, it is important to consider the development of precocious puberty for a prompt diagnosis and to strategize a multidisciplinary approach from the beginning.

DIAGNOSIS OF ENDOCRINE DISEASE: Mosaic disorders of FGF23 excess: Fibrous dysplasia/McCune-Albright syndrome and cutaneous skeletal hypophosphatemia syndrome

Fibrous dysplasia/McCune-Albright Syndrome (FD/MAS), arising from gain-of-function mutations in Gαs, and cutaneous skeletal hypophosphatemia syndrome (CSHS), arising from gain-of-function mutations in the Ras/MAPK pathway, are strikingly complex, mosaic diseases with overlapping phenotypes. Both disorders are defined by mosaic skin and bone involvement, and both are complicated by increased FGF23 production. These similarities have frequently led to mis-diagnoses, primarily in patients with CSHS who are often assumed to have FD/MAS. The intriguing similarities in skeletal involvement in these genetically distinct disorders have led to novel insights into FGF23 physiology, making an understanding of FD/MAS and CSHS relevant to both clinicians and researchers interested in bone and endocrine disorders. This review will give an overview of FD/MAS and CSHS, focusing on the roles of mosaicism and FGF23 in the pathogenesis and clinical presentation of these disorders.

Further delineation of the phenotypic spectrum of nevus comedonicus syndrome to include congenital pulmonary airway malformation of the lung and aneurysm

Nevus comedonicus syndrome (NCS) is a rare epidermal nevus syndrome characterized by ocular, skeletal, and central nervous system anomalies. We present a 23-month-old boy with a history of a congenital pulmonary airway malformation (CPAM) of the lung and a congenital cataract who developed progressive linear and curvilinear plaques of dilated follicular openings with keratin plugs (comedones) on parts of his scalp, face, and body consistent with nevus comedonicus. MRI of the brain demonstrated an aneurysm of the right internal carotid artery. Genetic testing identified NEK9 c.1755_1757del (p.Thr586del) at mean allele frequency of 28% in the nevus comedonicus. This same mutation was present in the CPAM tissue. This is the first case of a CPAM in a patient with an epidermal nevus syndrome. This case expands the phenotype of nevus comedonicus syndrome to include CPAM and vascular anomalies.

What's New in Genetic Skin Diseases

The discoveries of new genes underlying genetic skin diseases have occurred at a rapid pace, supported by advances in DNA sequencing technologies. These discoveries have translated to an improved understanding of disease mechanisms at a molecular level and identified new therapeutic options based on molecular targets. This article highlights just a few of these recent discoveries for a diverse group of skin diseases, including tuberous sclerosis complex, ichthyoses, overgrowth syndromes, interferonopathies, and basal cell nevus syndrome, and how this has translated into novel targeted therapies and improved patient care.

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.