Clinicopathologic features of 28 cases of nail matrix nevi (NMNs) in Asians: Comparison between children and adults

Subungual melanoma: molecular analysis of 31 cases from early stage to invasive melanoma

AIMS

The distinction between the benign subungual melanocytic lesions and an early lesion of subungual melanoma (SUM) remains a diagnostic challenge. We evaluated the routine diagnostic utility of array Comparative Genomic Hybridization (aCGH) to detect whole-genome copy number variations (CNV) as well as targeted next-generation sequencing (NGS) in SUM.

METHODS AND RESULTS

This retrospective study included 20 cases of in situ SUM and 11 cases of invasive SUM. Analysis by aCGH detected common oncogene amplifications in all but one case of invasive SUM (n = 10) and in all cases of in situ SUM with a melanocyte count (MC) >45/mm (n = 4 true positive) and the average number of CNV was 8.5. Thirteen remaining cases of in situ SUM gave false negative results (n = 13), owing to a lack of sufficient melanocytes to analyse (median MC of 35.35; range: 10.16-39.5). Molecular analysis failed in four cases (three in situ SUM and one invasive SUM) due to insufficient amounts of DNA. Across the whole cohort, the sensitivity of aCGH was 52%, but when adjusting the cutoff to MC >45/mm, the sensitivity was 93%. Targeted NGS was less informative than aCGH analyses in our series of SUM.

CONCLUSION

To distinguish malignant from benign lesions, especially in situ SUM versus atypical lentiginous melanocytic proliferations, aCGH analysis should be performed when the MC is above 45 melanocytes per linear millimetre. This pangenomic method can detect oncogene amplifications, as well as a number of CNV >3, which strongly support the diagnosis of malignancy.

Melanoma-like features in pediatric longitudinal melanonychia: A systematic review and meta-analysis

BACKGROUND

Pediatric longitudinal melanonychia (LM) can exhibit atypical features that mimic red-flag signs for subungual melanoma in adults and lead to diagnostic uncertainty. Nail biopsy may be unnecessary if clinical inspection and dermoscopy suggest a benign nature.

METHODS

We searched PubMed and Embase from inception to February 2023 for studies of any design reporting either the number or proportion of clinical and dermoscopic features in at least five children (≤18 years) with LM. Non-English articles, reviews, and abstracts were excluded. We performed a systematic review and meta-analysis to collate all existing data.

RESULTS

A total of 1218 articles were screened and 24 studies with 1391 pediatric patients were included. Nevus was the most common diagnosis (86.3%). The most prevalent sites were fingernails (76.2%) and first digits (45.4%). Pooled proportions of common features were: dark-color bands (69.8%), multi-colored bands (47.6%), broad bandwidth (41.1%), pseudo-Hutchinson sign (41.0%), irregular patterns (38.1%), Hutchinson sign (23.7%), dots and globules (22.5%), nail dystrophy (18.2%), and triangular sign (10.9%). Outcomes included progression (widening or darkening, 29.9%), stability (23.3%), and spontaneous regression (narrowing or fading, 19.9%). Only eight cases of subungual melanoma in situ were reported, and no invasive melanomas were identified.

CONCLUSION

Although atypical characteristics are common in pediatric LM, the probability of malignant transformation is exceedingly low. Appropriate evaluation and management of pediatric LM includes careful clinical and dermoscopic inspection with attention to benign features followed by long-term interval follow-up.

Clinical and Histopathological Investigation of Pediatric Melanonychia: A Single-Center Retrospective Case Series

HYPOTHESIS

The natural history of pediatric melanonychia and the necessity of biopsy for ruling out melanoma are debated in the literature. We hypothesize that there is a low rate of malignant nail pathology among pediatric patients undergoing nail bed biopsy for melanonychia.

METHODS

We performed a retrospective chart review of 54 pediatric patients (age <18 years) at a single institution who presented with melanonychia and underwent nail bed biopsy from 2007 to 2022. Data points collected included patient demographics, medical history, physical exam findings, pathology reports, and clinical photos. Univariate and multivariate analyses were performed to assess for risk factors associated with high-risk pathology findings.

RESULTS

The average age of melanonychia onset was 5.5 years (SD 4.4). The average age of first biopsy was 7.8 years (SD 4.3). On physical exam, 27 patients had at least four features concerning for melanoma (asymmetry, border irregularity, color heterogeneity, diameter > 1/3 of nail, evolving color, evolving diameter, Hutchinson's sign). The most common pathology diagnoses were melanocytic nevus (35%), atypical intraepidermal melanocytic proliferation (AIMP) with benign features (24%), subungual lentigo (22%), and AIMP with concerning features (17%). There were no cases of melanoma in situ or invasive malignant melanoma. On multivariate regression, the only significant risk factor associated with more concerning pathology (AIMP with concerning features) was the calendar year in which biopsy was performed (coefficient = -0.34, P = 0.016). There was no association between physical exam features and high-risk pathology. Twelve patients had surgical re-excision of the lesion, 6 of which were due to incomplete excision of AIMP with concerning features and 6 of which were due to recurrence.

CONCLUSIONS

Our case series did not find any cases of melanoma in situ or malignant melanoma arising from pediatric melanonychia. Atypical intraepidermal melanocytic proliferation with concerning features was associated only with the year in which the biopsy was performed, which may reflect the improved understanding of pediatric melanonychia as often benign despite concerning features on pathology. The decision to perform a nail matrix biopsy in pediatric melanonychia should be based on a collaborative discussion between the patient's parents, dermatologist, and plastic surgeon.

Adult and Pediatric Nail Unit Melanoma: Epidemiology, Diagnosis, and Treatment

Nail unit melanoma (NUM) is an uncommon form of melanoma and is often diagnosed at later stages. Approximately two-thirds of NUMs are present clinically as longitudinal melanonychia, but longitudinal melanonychia has a broad differential diagnosis. Clinical examination and dermoscopy are valuable for identifying nail findings concerning malignancy, but a biopsy with histopathology is necessary to confirm a diagnosis of NUM. Surgical treatment options for NUM include en bloc excision, digit amputation, and Mohs micrographic surgery. Newer treatments for advanced NUM include targeted and immune systemic therapies. NUM in pediatric patients is extremely rare and diagnosis is challenging since both qualitative and quantitative parameters have only been studied in adults. There is currently no consensus on management in children; for less concerning melanonychia, some physicians recommend close follow-up. However, some dermatologists argue that the "wait and see" approach can cause delayed diagnosis. This article serves to enhance the familiarity of NUM by highlighting its etiology, clinical presentations, diagnosis, and treatment options in both adults and children.

Dermatoscopic and clinical features of congenital or congenital-type nail matrix nevi: A multicenter prospective cohort study by the International Dermoscopy Society

BACKGROUND

Congenital nail matrix nevi (NMN) are difficult to diagnose because they feature clinical characteristics suggestive of adult subungual melanoma. Nail matrix biopsy is difficult to perform, especially in children.

OBJECTIVE

To describe the initial clinical and dermatoscopic features of NMN appearing at birth (congenital) or after birth but before the age of 5 years (congenital-type).

METHODS

We conducted a prospective, international, and consecutive data collection in 102 hospitals or private medical offices across 30 countries from 2009 to 2019.

RESULTS

There were 69 congenital and 161 congenital-type NMNs. Congenital and congenital-type NMN predominantly displayed an irregular pattern of longitudinal microlines (n = 146, 64%), reminiscent of subungual melanoma in adults. The distal fibrillar ("brush-like") pattern, present in 63 patients (27.8%), was more frequently encountered in congenital NMN than in congenital-type NMN (P = .012). Moreover, congenital NMN more frequently displayed a periungual pigmentation (P = .029) and Hutchinson's sign (P = .027) than did congenital-type NMN.

LIMITATIONS

Lack of systematic biopsy-proven diagnosis and heterogeneity of clinical and dermatoscopic photographs.

CONCLUSION

Congenital and congenital-type NMN showed worrisome clinical and dermatoscopic features similar to those observed in adulthood subungual melanoma. The distal fibrillar ("brush-like") pattern is a suggestive feature of congenital and congenital-type NMN.

Acral Melanocytic Neoplasms: A Comprehensive Review of Acral Nevus and Acral Melanoma in Asian Perspective

Acral melanocytic neoplasms, including acral melanocytic nevus and acral melanoma, are common melanocytic lesions in Asian populations. Both lesions occur on the volar surface of the hands and feet, and on nail units. Acral melanocytic nevi occur on the arch area of the sole, whereas acral melanomas frequently occur on weight-bearing areas of the sole, and on the fingernails. Therefore, the development of acral melanoma may be associated with chronic pressure, physical stress, or trauma. Dermoscopy is a useful adjunctive diagnostic tool for differential diagnosis. Acral melanocytic nevus is characterized by a parallel furrow pattern, whereas acral melanoma has a parallel ridge pattern. Genetic alterations are also different between the two types of lesion. BRAF and NRAS mutations are common in acral melanocytic nevus, whereas acral melanoma shows lower rates of KIT, NF1, BRAF, and NRAS mutations and remarkable copy number variations in genes such as CCND1, CDK4, hTERT, PAK1, and GAB2. Sentinel lymph node biopsy is important for staging and prognosis. Contemporary treatments for melanoma include targeted therapy for mutations and immunotherapy, such as anti-PD1 inhibitors.

Causes of longitudinal nail splitting: a retrospective 56-case series with clinical pathological correlation

BACKGROUND

Split nail (SN) is a rare type of nail fragility syndrome, characterized by a longitudinal fissure involving the entire thickness of the nail plate. Longitudinal nail splitting may be caused by direct injury to the nail plate or matrix insult. Few articles have been published on the topic, most were related to the traumatic aetiology. Some case reports mention tumours and inflammatory disorders as other causes.

OBJECTIVES AND METHODS

The aim of this retrospective study was to analyse the clinical and histopathological features of 56 SN collected at the nail consultation of the dermatology department at Saint Pierre University Hospital in Brussels, between 1997 and 2019.

RESULTS

Fifty-six patients were included (34 women and 22 men) with median age of 44.2 years. The fingernails were 3.2 times more frequently affected than toenails, especially the thumb. The most frequent aetiologies were tumours (45.6%), inflammatory diseases (26.3%) and traumas (19.3%). Congenital (5.3%) and systemic disorders (3.5%) were rarer causes. Histopathological slide review confirmed that alteration of the nail matrix integrity causes split nail, resulting either from matrix stretching by an underlying tumour or from impairment of the keratinization process by inflammatory diseases, melanocytic tumours and Bowen's disease.

CONCLUSIONS

This study is the largest case series of longitudinal nail splitting to date. It is the first to gather nail disorders causing SN with their clinical pathological correlation. The most common causes are traumatisms, tumours and inflammatory disorders. Congenital and systemic disorders are rarer. Tumours are responsible for half of the cases from which one third are malignant, mainly melanoma. When facing a monodactylic SN, benign as well as malignant tumours should be ruled out before concluding to traumatic aetiology.

Subungual Melanocytic Lesions in Pediatric Patients

The study of subungual melanocytic lesions can present challenges because of the clinical and histologic characteristics of the nail unit and the difficulty of performing nail biopsies and processing specimens. These lesions can be even more challenging in children due to differences in clinical and epidemiological profiles between the adult and pediatric populations. Many of the clinical features of subungual melanocytic lesions that would raise alarm in an adult do not have the same implications in children. Consensus is also lacking on when a nail biopsy is needed to rule out malignancy in the pediatric setting. In view of these considerations and the rarity of subungual melanoma in childhood, the recommended approach in most cases is a watch-and-wait strategy. Subungual melanocytic lesions in children may also show atypical histopathologic features that are not necessarily associated with aggressive behavior. Subungual melanoma is very rare in childhood, with just 21 cases described to date. None of the patients developed visceral metastasis or died as a result and the diagnosis was controversial in many of the cases. Considering the above and the significantly higher frequency and particular characteristics of longitudinal melanonychia with a benign etiology in children, subungual melanocytic lesions should be managed differently in this setting than in adults. In most cases, a watch-and-wait approach is the most appropriate strategy.

Equivocal Longitudinal Melanonychia in a 3-Year-Old Caucasian Girl: Rapid Evolution and Fading during Digital Dermoscopy Follow-Up

Introduction

Nail matrix nevi (NMN) in pediatric patients manifest as longitudinal melanonychia (LM) and can share clinical, dermoscopic, and histopathological characteristics with subungual melanoma. Equivocal findings in childhood LM may reflect dynamic processes during the natural life cycle of NMN in children.

Case Presentation

We present a case of a heavily pigmented LM with equivocal clinical and dermoscopic findings in a 3-year-old Caucasian girl, which exhibited signs of evolution, maturation, and almost complete involution within a short time period during digital follow-up, attributed to the natural course of NMN.

Discussion/Conclusion

Considering the rarity of subungual melanoma in childhood, our case underlines the significance of clinical and digital dermoscopy follow-up in the evaluation of childhood LM in order to avoid unnecessary biopsies and potential permanent nail dystrophy.

An Evidence-Based Approach to Pediatric Melanonychia

Melanonychia including melanonychia striata in children poses a diagnostic dilemma. Atypical clinical features often raise the possibility of malignancy, and a nail unit biopsy may be recommended. Commensurate with atypical clinical features, the histopathology may also appear alarming. However, accumulating data illustrate that most cases of melanonychia striata are benign and suggest that an alternate approach is often warranted for pediatric patients. Herein, we review the existing data regarding pediatric melanonychia striata and offer an evidence-based approach to its evaluation and management.

Dermoscopic Evaluation of Longitudinal Melanonychia in Children: A Prospective Study

Background:

Longitudinal melanonychia (LM) is a worrisome sign in both children and adults. Nail apparatus melanoma (NAM) can be related to LM, but it is very rare in children. Dermoscopic signs of benign lesions in children can be similar to melanoma; therefore, it is important to review dermoscopy of LM in children to make the best decision in performing biopsy.

Aims:

Biopsy taking is very challenging in LM in children. Most lesions are benign in children. The aim of this study was to review dermoscopic signs of LM in children and compare them with adults.

Materials and Methods:

In this prospective study a total of 108 LM (35 children and 73 adults) were undergone dermoscopy of LM. Dermoscopic features were compared in children and adults; both for benign lesions proven by biopsy or follow up and melanomas diagnosed histopathologically.

Results:

Black background, black band color, band color diversity and pseudo-Hutchinson's sign were more frequent in children in comparison with benign adult melanonychia. Some children's dermoscopic features of LM such as broad band width, Band color diversity, Hutchinson's sign, gray band color, asymmetry of pattern, and regression were similar to melanoma, but we did not find any melanoma by biopsy and/or follow up among children. We also detected the newly described "zigzag" pattern in four children.

Conclusion:

Dermatologists should consider all dermoscopic features of a lesion, dermoscopic sign changes in follow-up, medical, and familial history of the patient in deciding to perform biopsy of LM in children.

Nail discoloration in pediatric skin of color patients

Nail pigmentation in children can cause significant anxiety in parents and clinicians. Different pigments of the nails, such as yellow, orange, and green, can all occur; however, this paper will focus on the dark pigments: brown, gray, and black pigmentation of the nails. Many causes of dark coloration of the nails exist; almost all causes in pediatric patients are benign and require no treatment. Melanoma is the one diagnosis that physicians do not want to miss. Fortunately, this is extremely rare in children.

Review article: Emerging issues in pediatric skin of color, Part 2

Dermatology for pediatric skin of color is the application of dermatology to the genetically diverse and distinctive segment of the pediatric population that includes children of non-White racial and ethnic groups with increased pigmentation including individuals of Asian, Hispanic/LatinX, African, Native American, Pacific Island descent, indigenous people among others with overlap in particular individuals, and mixtures thereof. The discipline of pediatric skin of color can be challenging with difficulty in diagnosis of common conditions due to underlying pigmentation, variations in common hair styling practices, and differences in demographics of cutaneous disease. Whereas some conditions are more common in children of color, other conditions have nuances in clinical appearance and therapeutics with regard to skin color. This article, the second of the series, focuses on inflammatory skin disease nuances, melanocytic disorders, and hypopigmented mycosis fungoides.

Distribution of cellular remnants of melanocytes in the nail plate: Clue to the diagnosis of subungual melanoma

BACKGROUND

Previous studies reported that cellular remnants in the nail plate could be a diagnostic clue for subungual melanoma (SUM). We sought to characterize the histopathologic features of cellular remnants in the nail plates of SUM patients.

METHODS

A retrospective case-control study was conducted in a single tertiary center from 2012 to 2019. Twenty-three patients with pathologically diagnosed SUM and eight nail matrix nevi (NMN) patients were recruited. The analysis of the nail plate specimens focused on large cellular remnants of melanocytes (LCRMs). Longitudinal linear density and vertical distribution pattern of the LCRMs were scrutinized for possible features distinguishing SUM from NMN.

RESULTS

The median linear density of the LCRMs was significantly higher in the SUM samples than in the NMN samples. LCRMs in the SUM samples were more dorsally distributed than those in the NMN samples. In invasive SUM, LCRMs were more likely to be found in the dorsal part of the nail plate compared to SUM in situ.

CONCLUSION

Nail plate specimens should not be overlooked in the histopathological examination of melanonychia. High-density LCRMs with more dispersion to the dorsal side might be suggestive of SUM.

Melanocytic nevi on the hyponychium with dermoscopic features of longitudinal brush pigmentation in children

The dermoscopic features of longitudinally aligned pigmentation on the hyponychium were previously described in pediatric patients with longitudinal melanonychia. We report four cases of biopsy-proven acral melanocytic nevi on the hyponychium with a longitudinal brush pigmentation (LBP) pattern in dermoscopy. This LBP pattern on the hyponychium may be a counterpart of the fibrillar pattern of acral melanocytic nevi. Therefore, the LBP pattern in dermoscopy may provide a useful clue for distinguishing benign melanocytic nevi from melanoma in pediatric patients.

Clinicopathological diversity and outcome of longitudinal melanonychia in children and adolescents: analysis of 35 cases identified by excision specimens

AIMS

Longitudinal melanonychia in paediatric patients often represents a difficult diagnostic challenge, and studies emphasising its clinical and histopathological features are limited due to its low incidence in childhood.

METHODS AND RESULTS

We retrospectively analysed 35 paediatric cases identified by excision specimens on their clinicopathological features, and performed fluorescence in-situ hybridisation on 13 available cases. Fingernails (77.1%) were more likely to be affected. Total melanonychia and Hutchinson's sign were observed in 10 (28.6%) and 14 (40.0%) cases, respectively. Nail dystrophy at diagnosis was present in five cases. After complete excision of the lesions, four patients relapsed during follow-up (mean = 38 months). Seventeen cases were diagnosed as lentigines and 18 as naevi, among which 11 cases were categorised as lentigines/naevi with atypical melanocytic hyperplasia. Mild-to-moderate nuclear atypia, confluency of melanocytes, focal pagetoid spread and peri-ungual skin involvement were found in 25.7% (9 of 35), 40.0% (14 of 35), 40.0% (14 of 35) and 40.0% (14 of 35) of cases, respectively. Thirteen cases tested by fluorescence in-situ hybridisation showed no copy number aberration at the probed loci. There was a statistically significant difference in the following features between patients aged less and more than 10 years (P < 0.05): cytomorphology, mild-to-moderate nuclear atypia, confluency of melanocytes, focal pagetoid spread and melanocyte count.

CONCLUSIONS

Some concerning clinicopathological characteristics, which are signs indicative of melanoma in adults, are not uncommon in paediatric longitudinal melanonychia, especially in patients aged ≤ 10 years. Owing to the extremely low incidence of melanoma in paediatric longitudinal melanonychia, in most circumstances a more conservative clinical management strategy should be adopted.

Updates on the Pathology and Management of Nail Unit Tumors and Dermatoses

Nail unit pathology is indispensable to reach an accurate diagnosis of nail tumors as well as inflammatory disorders. This review article provides an update from the most recently published studies on the pathology and management of nail unit tumors and inflammatory disorders. Recent findings of nail clipping histopathology are described first, followed by discussing recent data on the diagnosis and surgical management of several types of nail unit tumors, ending with discussing the recent discoveries in selected nail unit inflammatory disorders.

Subungual Melanocytic Lesions: Key Clinical and Pathologic Concepts and Biopsy Techniques

Both dermatologists and pathologists sometimes find daunting the evaluation of melanonychia (especially subungual melanocytic lesions) because of the fear of performing nail surgery due to the risk of dystrophy, difficulties processing and interpreting nail biopsy specimens, and a general lack of experience in the field. Nevertheless, mastery of nail biopsy techniques, correct processing and orientation of specimens, and familiarity with the histologic particularities of the nail apparatus can attenuate the undoubted complexity and facilitate the tasks involved. Longitudinal excision is the biopsy technique that ensures the simplest histologic interpretation, and it is associated with a low risk of nail dystrophy when performed correctly. Clinical and epidemiological data are crucial. Subungual melanoma in childhood, for instance, is very rare and even lesions with atypical clinical and/or histologic features are probably benign. The presence of suprabasal melanocytes and other findings that would suggest malignancy at other sites are considered normal in the nail apparatus. Subungual melanoma shows a lentiginous pattern in the early stages of disease, and detection of an inflammatory infiltrate accompanying atypical lentiginous subungual lesions would appear to be one of the first diagnostic findings.

Pathology of the Nail Unit

This article discusses the histologic findings in key nail unit diseases, including inflammatory, infectious, and neoplastic conditions. The emphasis is on clinicopathologic correlates, best practices to demonstrate the relevant histopathologic features, and pitfalls in diagnosis. Understanding the pathology of these disorders enhances clinical acumen and may affect the choice of biopsy procedures and treatment measures, with the outcome of better clinical care for patients with nail disease.

Subungual Melanocytic Lesions: Key Clinical and Pathologic Concepts and Biopsy Techniques

Both dermatologists and pathologists sometimes find daunting the evaluation of melanonychia (especially subungual melanocytic lesions) because of the fear of performing nail surgery due to the risk of dystrophy, difficulties processing and interpreting nail biopsy specimens, and a general lack of experience in the field. Nevertheless, mastery of nail biopsy techniques, correct processing and orientation of specimens, and familiarity with the histologic particularities of the nail apparatus can attenuate the undoubted complexity and facilitate the tasks involved. Longitudinal excision is the biopsy technique that ensures the simplest histologic interpretation, and it is associated with a low risk of nail dystrophy when performed correctly. Clinical and epidemiological data are crucial. Subungual melanoma in childhood, for instance, is very rare and even lesions with atypical clinical and/or histologic features are probably benign. The presence of suprabasal melanocytes and other findings that would suggest malignancy at other sites are considered normal in the nail apparatus. Subungual melanoma shows a lentiginous pattern in the early stages of disease, and detection of an inflammatory infiltrate accompanying atypical lentiginous subungual lesions would appear to be one of the first diagnostic findings.

Pediatric nail disorders: a review

PURPOSE OF REVIEW

Nail disorders represent an uncommon subset of complaints seen in pediatric dermatology. There is a wide array of disorders that can affect the nail unit in children, including infectious, inflammatory, neoplastic, congenital, and traumatic processes. In order to enhance familiarity with pediatric nail conditions, we review the background and treatment of the more common entities seen in pediatric onychology, including onychomycosis, onychomadesis, nail psoriasis, trachyonychia, longitudinal melanonychia, onychophagia, and onychocryptosis.

RECENT FINDINGS

Nail involvement in pediatric patients with psoriasis may indicate increased risk for both overall disease severity and the development psoriatic arthritis. In the evaluation of longitudinal melanonychia, the clinical findings that raise concern for subungual melanoma in adults are often found in benign nail unit nevi in children. In the systemic treatment of pediatric onychomycosis, new data raises the possibility that laboratory monitoring may be approached differently. In the approach to onychophagia, emerging pharmacotherapies include N-acetylcysteine.

SUMMARY

Most nail disorders in pediatric patients have an overall favorable prognosis. However, nail abnormalities can lead to patient and parental anxiety, decreased quality of life, pain, and functional impairment. Clinicians should be aware of these more common diverse entities in order to identify them and apply state of the art management for these issues. Additionally, the reader will learn factors related to these nail disorders, which may require systemic work-up and/or specialist referral.

Oral and nail pigmentations: a useful parallelism for the clinician

Oral (OP) and nail (NP) pigmentations may occur simultaneously in physiological or pathological conditions, and may be a sign of underlying syndromic conditions that necessitate further investigation and treatment. Interestingly, the nail unit and oral cavity show a clinical parallelism that may help the clinician to conduct a correct examination and reach a prompt diagnosis. Both OP and NP can manifest clinically with focal or diffuse involvement and are due to external factors (exogenous pigmentation, drug-induced pigmentation) or endogenous factors (racial pigmentation, post-inflammatory pigmentation, nevi, genetic conditions and other disorders). The most concerning differential diagnosis is melanoma. Here we report the pathogenetic basis of OP and NP, together with the description of similar clinical features. To the best of our knowledge this is the first paper to summarize and describe the causes of pigmentation of both the oral cavity and the nail unit.