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This report describes the clinical, onychoscopic, nail clipping, and histopathologic features of a malignant onychopapilloma. A 71-year-old male presented to our outpatient clinic for a stable, asymptomatic lesion on his left middle finger that had been present for 2 years. Prior nail clipping histopathology showed nail plate thinning with subungual abnormal onychocytes. Clinical examination revealed a 2-mm-wide streak of longitudinal xanthonychia extending to the proximal nail fold, with distal hyperkeratosis and onycholysis. Onychoscopy showed irregular longitudinal nail plate ridging with scattered punctate hemorrhagic foci. An excisional nail unit biopsy demonstrated cellular atypia of the nail bed epithelium, matrix metaplasia, longitudinal abnormal onychocytes, increased Ki-67 staining, and negative HPV immunoperoxidase staining, confirming the diagnosis of malignant onychopapilloma., (© 2024 The Authors. Journal of Cutaneous Pathology published by John Wiley & Sons Ltd.)

Melanoma of the nail apparatus is challenging to diagnose for both dermatologists and dermatopathologists. Misdiagnosis or delayed diagnosis of nail unit melanoma can have fatal consequences and legal ramifications. This review educates dermatopathologists on challenges and traps they should be aware of to avoid misdiagnosis of nail unit melanoma. We present illustrative difficult cases that introduce several themes regarding challenges in the diagnosis of nail unit melanoma: specimens with subtle histopathologic findings, challenges in immunoperoxidase interpretation, and how clinical knowledge and surgical procedural knowledge are mandatory to make the diagnosis. Dermatopathologists will be aware of when and how to suspect nail unit melanoma in unusual circumstances., (© 2023 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

We call on dermatologists and dermatopathologists to include nail clipping histopathology as an essential component of the routine evaluation of melanonychia. This manuscript demonstrates a case where an adult woman with broad melanonychia of the right thumbnail declined a nail matrix biopsy, but was amenable to a nail clipping.The nail clipping showed pigmentation, melanocyte remnants, and small cavities in the nail plate. These features have been published previously by our group as a clue to nail unit melanoma within nail clippings.This patient was rapidly triaged for nail matrix biopsy, which demonstrated nail unit melanoma in situ. Every patient with melanonychia can benefit from a nail clipping by examination of the location of the pigmentation within the nail plate for surgical planning, and if melanocyte remnants are detected, the nail clipping also serves as a rapid triage mechanism for nail matrix biopsy to evaluate for nail unit melanoma. Fontana-stained sections will highlight the pigmentation in the nail plate, and its location in the nail plate can easily be described by the dermatopathologist. Nail clippings performed in the setting of clinically apparent melanonychia may show helpful histopathologic findings of pigmented fungi, hemorrhage, external pigmentation, features of other pigmented nail unit tumors, as well as other entities. Nail clipping histopathology can provide extensive information in the evaluation of melanonychia with minimal discomfort for a patient, and little disruption to a physician's clinic flow. With this additional case of a nail unit melanoma diagnosed after initial concern found in a nail clipping, as well as other information in the literature, it is clear that melanocyte remnants found in nail clippings are reliable concerning features related to nail unit melanoma in adults. With knowledge of these histopathologic features in nail clippings and the significance of melanocyte remnants, the dermatopathologist can play a crucial role in the use of a nail clipping as a life-saving diagnostic maneuver. Accordingly, given the potential benefit to patients in this setting, as well as other uses of a nail clipping in the evaluation of melanonychia, we call on dermatologists and dermatopathologists to innovate the routine evaluation of melanonychia through the routine employment of nail clippings for histopathologic evaluation., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

A 7-year-old healthy girl presented with an 11-month history of an asymptomatic red, dome-shaped papule on her right medial elbow and 6-month history of linearly distributed, few millimeter, flesh-colored papules extending from and including the red papule. Histopathology demonstrated features of both a Spitz nevus and lichen striatus. The Spitz nevus was removed with a punch biopsy and the lichen striatus subsequently resolved. To our knowledge, co-localization of a Spitz nevus with lichen striatus has not been previously reported and highlights the potential association between the immunogenicity of Spitz nevi and the development of lichen striatus., (© 2021 Wiley Periodicals LLC.)

Subcutaneous fat necrosis (SCFN) is an inflammatory disorder of the adipose tissue that commonly presents in neonates as tender subcutaneous nodules on the trunk and extremities with hypercalcemia as a potential complication. We report the case of a 3-month-old female who presented with circular alopecia of the scalp and was found to have histopathologically confirmed SCFN. Recognition of SCFN as a cause for alopecia in young infants may allow prompt screening for hypercalcemia and reduce the risk for associated morbidity and mortality., (© 2021 Wiley Periodicals LLC.)

A 6-year-old boy with severe very early-onset inflammatory bowel disease (VEO-IBD) was admitted for 1 week of high fevers, loose stools, joint pains, and myalgias. He subsequently developed a progressive, papular, and vesiculopustular eruption on his face with rapid spread to his trunk and extremities. Histopathology demonstrated dense dermal neutrophilic inflammation. Findings were consistent with bowel-associated dermatosis-arthritis syndrome (BADAS), which is rarely reported in children and requires further characterization., (© 2021 Wiley Periodicals LLC.)

Basal cell nevus syndrome (BCNS) is an autosomal dominant condition caused most often by a loss-of-function mutation in the Patched-1 (PTCH1) gene. It is characterized by the development of varied benign and malignant tumors, including numerous cutaneous basal cell carcinomas (BCCs). The PTCH1 gene is integral in hair follicle development and loss of function mutation may lead to BCCs with an infundibulocystic histopathology in BCNS patients. Few studies have described the histopathological features of BCCs in BCNS. The recognition of these histopathologic features by dermatologists, dermatopathologists, and others caring for children will allow earlier and more effective identification of BCNS. We performed a retrospective analysis of 25 BCCs in 11 patients aged 5 to 19 years with BCNS and evaluated the histopathologic features on hematoxylin-eosin-stained sections. Our study found that 80% of BCCs in BCNS patients occurred on the head and neck with 64% of the specimens demonstrating infundibulocystic differentiation. Infundibulocystic differentiation is a common finding in BCCs found in BCNS. The finding of cutaneous neoplasms consistent with BCC with infundibulocystic differentiation in children is common in pediatric patients with BCNS and can be considered to be an early marker of the disorder, prompting further clinical investigation., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background/objectives: Head and neck dermatitis after dupilumab therapy for atopic dermatitis has been frequently reported in adults and only rarely in adolescents. No cases detailing disease course and treatment response have previously been described in adolescents., Methods/results: This case series presents five adolescent patients who developed new-onset or worsening head and neck dermatitis after dupilumab therapy for atopic dermatitis. All five patients improved after oral antifungal therapy., Conclusions: The clinical features, treatment response, and potential disease pathogenesis in pediatric patients are described. Adolescents with new-onset head and neck dermatitis after dupilumab therapy may clinically improve with antifungal therapy, suggesting that Malassezia species may be a contributing factor or antifungal therapy may be an effective antiinflammatory agent., (© 2020 Wiley Periodicals LLC.)

Background: Pachyonychia congenita (PC) is a rare autosomal dominant disorder of keratinization mediated by genetic mutations in KRT6A, KRT6B, KRT6C, KRT16, or KRT17. While nail dystrophy in PC has a significant impact on quality of life, the histopathological features of the nail plate in PC have not been previously reported. We report the histopathological features of nail plates provided by 19 patients with genetically confirmed PC., Methods: Nineteen patients with genetically confirmed PC provided a total of 56 nail plates for histopathologic examination. The nail plates were examined for the presence of hyphae, yeast, bacteria, neutrophils, parakeratosis, plasma globules, and hemorrhage. Specimens with onychomycosis (three patients) were excluded from the analysis., Results: No specific histopathological feature was identified in PC nails. Parakeratosis and plasma globules were the most prominent features in both clinically affected and unaffected PC nails. There was a significant association between clinical dystrophy of all 20 nails and KRT6A mutations, and a lack of dystrophy of all 20 nails in KRT6B mutations., Conclusions: Parakeratosis and plasma globules in the absence of other inflammatory disorders should raise PC in the histopathologic differential diagnosis. The presence of onychomycosis in a nail plate does not exclude a diagnosis of PC., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Verruciform xanthoma (VX) is a rare finding thought to be caused by epidermal damage from trauma or inflammation and has been reported in a limited number of patients with recessive dystrophic epidermolysis bullosa (RDEB). Herein, we describe a 20-year-old woman with RDEB who developed a large, verrucous, pink plaque on the posterior thigh that was histologically proven to be a VX. We review cases of VX in patients with RDEB and summarize the clinical features, pathophysiology, and management principles., (© 2019 Wiley Periodicals, Inc.)

Background/objectives: Lichen striatus is a unilateral inflammatory dermatosis that rarely affects the nail unit. When the inflammation involves the nail unit, classic lichenoid nail changes are easily detectable, more often limited to only one portion of the nail. Usually the nail dystrophy coexists with periungual skin papules following Blaschko's lines, but it could also be an isolated feature. Because a nail unit biopsy presents difficulties in execution, especially in a child, the aim of our study has been to describe the nail unit dermoscopy features of lichen striatus hoping to provide a valid aid to clinicians in the diagnosing this rare disorder., Methods: We reviewed the images of five pediatric patients with a clinical diagnosis of lichen striatus. Data about sex, age, localization, predisposing/triggering factors, and associated disorders are reported., Results: The diagnosis of lichen striatus can be challenging as there are clinically overlapping features with related dermatoses. A common diagnostic pitfall occurs with inflammatory linear verrucous epidermal nevus and lichen planus. Involvement of only one part of the nail plate with linear longitudinal fissuring, ridging, and distal splitting, especially if seen with perionychial skin lesions, is characteristic of lichen striatus., Conclusions: Nail lichen striatus is rare, and there is sparse published literature on it. When the changes in lichen striatus are limited to the nail, the diagnosis may easily be missed. We therefore believe that dermoscopy is an important diagnostic maneuver, which should be integrated into the evaluation of patients with potential lichen striatus, and in particular is helpful for clinicians unwilling or unable to perform a nail unit biopsy., (© 2019 Wiley Periodicals, Inc.)

Erosive pustular dermatosis of the scalp (EPDS) is an uncommon chronic inflammatory response to scalp trauma that usually resolves with cicatricial alopecia. It most commonly affects elderly patients with a history of actinic damage. Herein, we describe a 16-year-old girl with acrofacial dysostosis type 1 presenting after surgery with crusting purulent scalp lesions, whose clinical presentation and histopathologic findings were consistent with EPDS. A review of the literature on EPDS in children is also detailed., (© 2019 Wiley Periodicals, Inc.)

Chondrodermatitis nodularis helicis is an idiopathic degenerative process that presents as a painful nodule, papule, or ulcer on the helix or antihelix. It predominantly affects adults and is thought to be associated with trauma to the ear. We describe a case of pediatric chondrodermatitis nodularis helicis occurring in a child with a history of Beckwith-Wiedemann syndrome that was successfully treated with an excisional biopsy and relief from a recurrent source of pressure on the ear., (© 2019 Wiley Periodicals, Inc.)

Transverse melanonychia is a rare finding often secondary to chemotherapy, orally ingested medications, or other iatrogenic interventions. A 19-month-old boy with hemophagocytic lymphohistiocytosis treated with biweekly etoposide and dexamethasone developed transverse bands of pigment in all toenail and fingernail units consistent with transverse melanonychia. We review the literature for reported cases of transverse melanonychia and summarize suspected etiologies., (© 2018 Wiley Periodicals, Inc.)

Angiomatoid and desmoplastic Spitz nevi are rare histologic variants of Spitz nevi that present most frequently on the extremities of children and young adults. Although Spitz nevi are clinically heterogeneous, one presenting as a keloidal nodule has not been previously published. We present a case of an angiomatoid and desmoplastic Spitz nevus clinically akin to a keloid on an African-American teenager and describe its unique histopathologic features., (© 2018 Wiley Periodicals, Inc.)

Asymmetric hypertrophy of the labia minora is a variant of normal anatomy that has not been described in the pediatric dermatology literature. Although often asymptomatic, in some cases, it can cause functional, emotional, and psychological problems. We report the clinical characteristics and outcomes of four children who presented with unilateral labium minus hypertrophy. This case series aims to establish awareness of this condition among pediatric dermatologists and provide recommendations regarding management., (© 2018 Wiley Periodicals, Inc.)