Nevus comedonicus: an updated review

Nevus comedonicus: A case report with the histological findings and brief review of the literature

INTRODUCTION

Nevus comedonicus (NC) is a rare cutaneous disorder thought to be caused by hamartomatous pilosebaceous tissue proliferation that was first described in 1895. Clinically NC appears as a group of elevated follicular openings often linearly arrayed, giving the appearance of comedones. NC usually manifests at birth but can also present later during adolescence and rarely in adulthood.

CASE PRESENTATION

A 21-year-old medically healthy single male presented with right-sided chest black papules in comedo distribution with areas of superficial ulcerations and suppurations in periareolar distribution since the age of 16. Histopathological examination showed dilated follicular ostia filled with keratin plug, devoid of the hair shaft, and lined by stratified squamous epithelium with compact hyperkeratosis, focal parakeratosis, and patchy atrophy and acanthosis.

CLINICAL DISCUSSION

Nevus comedonicus often responds effectively to conservative treatment, however some cases need surgery intervention. The patient failed conservative medical and topical treatment, and he was treated by surgical-wide local excision and primary closure of the affected skin with free nipple grafting.

CONCLUSION

Nevus comedonicus (NC) is a rare cutaneous pathology secondary to pilosebaceous apparatus developmental defect that usually manifests at birth and can affect any area of skin; they typically manifest as black papules in comedo distribution. They can present as an isolated cutaneous pathology or as a component of nevus comedonicus syndrome. Different therapeutic approaches were described, including topical retinoids, keratolytic agents, oral retinoids, antibiotic therapy, manual extraction of comedos, dermabrasion, and surgical resection of the lesion.

Nevus Comedonicus Suppurativa: A Report of a Novel Entity

Nevus comedonicus and hidradenitis suppurativa (HS) are disorders of the pilosebaceous unit sharing a similar pathogenesis of follicular occlusion. To our knowledge, less than 10 cases of HS-like lesions complicating nevus comedonicus have been reported. We describe a six-year-old female child with congenital linear nevus comedonicus in the left axilla and groin, complicated by recurrent HS-like lesions in the two years prior to presenting to our clinic. After a meticulous review of the literature, we propose a novel term, nevus comedonicus suppurativa, for this clinical entity.

Mosaicism in genodermatoses

Genodermatoses are inherited disorders presenting with cutaneous manifestations with or without the involvement of other systems. The majority of these disorders, particularly in cases that present with a cutaneous patterning, may be explained in the context of genetic mosaicism. Despite the barriers to the genetic analysis of mosaic disorders, next-generation sequencing has led to a substantial progress in understanding their pathogenesis, which has significant implications for the clinical management and genetic counseling. Advances in paired and deep sequencing technologies in particular have made the study of mosaic disorders more feasible. In this review, we provide an overview of genetic mosaicism as well as mosaic cutaneous disorders and the techniques required to study them.

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.

Successful treatment of late-onset nevus comedonicus with Er:YAG laser

Nevus comedonicus, a rare congenital hamartoma of the pilosebaceous unit, is characterized by keratotic plugging. It usually occurs after birth and during early childhood. It rarely appears in adulthood. Despite the benign nature of the condition, it usually requires treatment due to aesthetic reasons. Several treatments have been reported in nevus comedonicus, most of them resulting with recurrences. Here, we report a case of nevus comedonicus with adult onset, successfully treated with erbium-doped yttrium aluminum garnet (Er:YAG) laser therapy.

Mutation and expression of ABCA12 in keratosis pilaris and nevus comedonicus

Keratosis pilaris (KP) and nevus comedonicus (NC) are congenital keratinized dermatoses; however, the exact etiology of these two diseases is unclear. The objective of the present study was to identify the disease-causing genes and their association with functional alterations in the development of KP and NC. Peripheral blood samples of one KP family, two NC families and 100 unrelated healthy controls were collected. The genomic sequences of 147 genes associated with 143 genetic skin diseases were initially analyzed from the KP proband using a custom-designed GeneChip. A novel heterozygous missense mutation in the ATP-binding cassette sub-family A member 12 (ABCA12) gene, designated c.6694G>T (p.Asp2232Tyr), was identified in the KP proband and confirmed by Sanger sequencing. The same mutation was also present in the affected family members but not in the healthy family members, the two patients with NC or population-matched controls. The predictions provided by PolyPhen-2 and SIFT analyses suggested that the mutation may produce a damaged protein. The region surrounding the mutation is the extra-membrane domain, which is conserved among particular species, as suggested by ClustalX; however, no ABCA12 mutations were reported in the patients with NC. As observed by immunofluorescence, ABCA12 expression was upregulated in the sebaceous glands of the patients with NC compared with that of normal controls. In summary, ABCA12-associated mutations or alterations in expression may exhibit causative or contributive effects to the development of keratinized dermatoses, including KP and NC.

Extensive Nevus Comedonicus, Complicated with Recurrent Abscesses, Successfully Treated with Surgical Resurfacing

Nevus comedonicus is a rare epidermal abnormality of the pilosebaceous unit, which is congenital in most patients but may also appear early in childhood. It may be localized or have an extensive involvement, the latter showing a unilateral predominance with only a few cases presenting bilaterally. Extensive nevus comedonicus can be associated with musculoskeletal defects, eye and neurological involvement, which constitutes nevus comedonicus syndrome. Uncomplicated nevus comedonicus can be treated with topical keratolytics, diode, erbium laser, and ultrapulse CO₂ laser. Surgical excision can be performed to ensure complete removal and nonrecurrence. This case report refers to a young male patient with extensive nevus comedonicus present over left chest, left axilla, and left upper back without systemic involvement, treated with staged surgical excision and resurfacing.

Nevus Comedonicus: Case Report

Nevus comedonicus is a rare cutaneous anomaly, characterized by the clustering of papules with firm, blackened horny buffers. It in general has a zosteriform pattern and affects both genders equally. In some patients, there is formation of cysts, abscesses, and fistulas, aggravating its psychosocial impact. The association with extracutaneous lesions characterizes the nevus comedonicus syndrome. Despite several therapeutic options, the result is unsatisfactory in most cases. We report the case of a man with an exuberant congenital lesion, affecting the left suprascapular region, arm, and forearm.

Multiple vulvar dilated pores in a postmenopausal woman

Winer's dilated pore is an infrequent appendageal tumor characterized by a giant comedone on the face, neck, and upper trunk in adults. We report a 57-year-old woman who developed multiple asymptomatic black papules on both labia majora. Histopathology showed grouped dilated follicles lined by keratinizing squamous epithelium in the superficial dermis. The superficial lining epithelium and interfollicular epidermis were atrophic, while the deep epithelium showed mild proliferation and melanin pigmentation with a few short projections extending into the surrounding dermis. We diagnosed multiple Winer's dilated pores based on late-onset lesions and pathological features. This patient may represent the first case of multiple vulvar Winer's dilated pores. We suggest that electrocautery may be effective for treating this type of superficial entity.

Hair Follicle Nevus With Features of Comedo Nevus: An Expanding Spectrum

Hair follicle nevus (HFN) is a rare hamartomatous lesion of the folliculosebaceous unit, with or without admixed fibroadipose or muscular tissue. It typically has a congenital presentation in the preauricular area of infants and is frequently confused with an accessory tragus. Acquired tumors with similar histopathologic features have been described infrequently during adolescence and adult life. We report yet another unique presentation of this unusual lesion in a 4-year-old girl who had a long-standing tumor of the nasal columella that started growing rapidly after trauma. Histopathologic examination revealed increased numbers of hair follicles, some of which were associated with diminutive sebaceous glands, with no associated central cystic structure. In addition, the infundibula of the follicles were dilated and filled with keratinous debris. Although these hamartomas are common in the head and neck region, to our knowledge, this is the first report of a HFN at this anatomic location. In addition, this tumor has an overall architecture of a HFN but is accompanied by features of a comedo nevus. We also present a review of the literature and summarize the current diagnostic criteria for HFN.

Somatic Mutations in NEK9 Cause Nevus Comedonicus

Acne vulgaris (AV) affects most adolescents, and of those affected, moderate to severe disease occurs in 20%. Comedones, follicular plugs consisting of desquamated keratinocytes and sebum, are central to its pathogenesis. Despite high heritability in first-degree relatives, AV genetic determinants remain incompletely understood. We therefore employed whole-exome sequencing (WES) in nevus comedonicus (NC), a rare disorder that features comedones and inflammatory acne cysts in localized, linear configurations. WES identified somatic NEK9 mutations, each affecting highly conserved residues within its kinase or RCC1 domains, in affected tissue of three out of three NC-affected subjects. All mutations are gain of function, resulting in increased phosphorylation at Thr210, a hallmark of NEK9 kinase activation. We found that comedo formation in NC is marked by loss of follicular differentiation markers, expansion of keratin-15-positive cells from localization within the bulge to the entire sub-bulge follicle and cyst, and ectopic expression of keratin 10, a marker of interfollicular differentiation not present in normal follicles. These findings suggest that NEK9 mutations in NC disrupt normal follicular differentiation and identify NEK9 as a potential regulator of follicular homeostasis.

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.

Extensive nevus comedonicus involving the palm: questionable role of the pilosebaceous unit in pathogenesis

A 10-year-old boy had multiple grouped pits with black plugs arranged along the lines of Blaschko on his left chest, arm, and palm. Involvement of the palms is rarely reported in the literature. Recent reports have described mosaic acneiform conditions that could share pathogenetic mechanisms with nevus comedonicus. We briefly review the literature on mosaic conditions with acneiform lesions including nevus comedonicus.

Nevus comedonicus in oral-facial-digital syndrome type 1: a new finding or overlapping syndromes?

We report a patient with oral-facial-digital syndrome type 1 (OFDS1) who exhibited features overlapping those of nevus comedonicus syndrome, an unusual presentation that may potentially represent a new variant of OFDS1. OFDS1 and nevus comedonicus syndrome represent two rare syndromes with numerous overlapping features that have yet to be described in relation to one another. The features present in our patient led us to propose the possibility of a new variant of OFDS1 in which nevus comedonicus represents a cutaneous manifestation of the syndrome. Knowledge of this potential relationship is important for identification and management of the syndromes' accompanying manifestations in affected patients and may offer further insight into crossroads of pathogenesis.