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. 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. 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. 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 (NC) is a rare developmental anomaly of the folliculosebaceous apparatus, which appears as numerous dilated papules containing firm, darkly pigmented, horny plugs. It appears shortly after birth and mostly before the age of 10; however, late-onset cases have been reported. There is no gender or racial predilection. Moreover, NC can be a component of nevus comedonicus syndrome, a neurocutaneous disorder with skeletal, ocular, and central nervous system abnormalities. EHK properties in NC are not a common finding and are rarely seen in association with each other. This paper reports a healthy, 27-year-old young woman who has been developing numbers of asymptomatic unilateral linear skin lesions on her chest, waist, right thigh, and popliteal fossa in a unilateral linear pattern over ten years. Skin biopsy revealed dilated follicular ostia with orthokeratotic hyperkeratosis, columns of parakeratosis, cornoid flagellation, epidermolytic hyperkeratosis, and mild acanthosis on its wall.

Nevus comedonicus (NC) is a rare hamartoma of the pilosebaceous unit origin. The association with extracutaneous abnormalities defines NC syndrome (NCS). Fewer than 50 cases of NCS have been reported in the English literature. A 31-year-old woman presented with grouped and linear comedonal papules present from birth and located on the left buttock along Blaschko's lines. She had a history of pediatric mood disorder combined with attention-deficit hyperactivity disorder (ADHD) from 5 years of age and was recently diagnosed with sinus bradycardia. Her skin lesion was surgically removed and microscopic findings revealed the aggregation of dilated follicular infundibula filled with prominent laminated keratin plugs, a characteristic finding of NC. This is the first report presenting NCS associated with mood disorder and ADHD. Psychiatric symptoms may represent systemic manifestation of NCS.

Benign skin tumors represent a wide category of diseases. The diagnosis is usually provided by the clinical aspect and the patient history. The pathological examination is not always considered necessary and in most cases the treatment is removal of the lesion by cryotherapy, electrosurgery or laser ablation. Deep phenotyping, including genetic and epigenetic findings, provided the basis of a new understanding of the pathogenetic mechanisms. Some benign skin tumors can be part of syndromes and the dermatologist should be aware of the extracutaneous associations defining these rare disorders: epidermal nevus can be associated with vascular malformations; nevus sebaceous can be associated with cerebral, ocular, and skeletal defects; nevus Becker is associated with cerebral, ocular, and skeletal defects; pilomatricomas appear earlier than colorectal cancer in Gardner's syndrome; tuberous sclerosis complex can associate not only central nervous system lesions but also pulmonary, cardiac or renal manifestations. Gutartige Hauttumoren kommen bei einer großen Zahl von Hautveränderungen vor. Die Diagnose wird in der Regel durch das klinische Bild und die Anamnese gestellt. Eine histopathologische Untersuchung ist nicht in jedem Fall zwingend erforderlich. Die Therapie besteht meistens in der Entfernung der Hautveränderungen durch Kryotherapie, Elektrochirurgie oder Laserabtragung. Differenzierte Phänotypisierungen einschließlich genetischer und epigenetischer Befunde liefern die Grundlage für ein neues Verständnis der pathogenetischen Mechanismen. Einige gutartige Hauttumoren können Teil von Syndromen sein, daher sollten Zusammenhänge mit nichtdermatologischen Befunden bekannt sein, die diese seltenen Erkrankungen charakterisieren. Der epidermale Nävus kann mit Gefäßmalformationen in Beziehung stehen, der Naevus sebaceus sowie der Becker-Nävus mit Defekten zerebral, okulär und am Skelett, Pilomatrixome können kolorektalen Karzinomen beim Gardner-Syndrom vorangehen, tuberöse Sklerose kann assoziiert sein nicht nur mit Veränderungen im Zentralnervensystem, sondern auch an Lunge, Herz oder Nieren.

Nevus comedonicus (NC) syndrome is a condition first identified in 1978. The cause of NC syndrome has been recently proven to be a gain-of-function, mosaic postzygotic mutation of the NEK9 gene. A systematic review of the literature retrieved 43 well-established cases of NC syndrome reported so far. Three morphological variants of NC in NC syndrome emerged: (a) the more common, predominantly comedonal type; (b) "Selhorst type"; and (c) "atrophoderma vermiculatum" type. NC syndrome is mainly associated with ocular, skeletal, and neural abnormalities, most typically ipsilateral congenital cataract and malformations of fingers and toes.