Wikipedia

Melanonychia

Melanonychiais a black or brown pigmentation of anail,and may be present as a normal finding on many digits in Afro-Caribbeans, as a result of trauma, systemic disease, or medications, or as a postinflammatory event from such localized events aslichen planusorfixed drug eruption.[1]: 790 [2]: 665 

Melanonychia
SpecialtyDermatology

There are two types, longitudinal and transverse melanonychia.[2]: 671 

Signs and symptoms

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Melanonychia is defined by a darkening of the nail plate that is brown to black; the pigment in question is typicallymelanin.It can affect one or more fingernails as well as toenails.[3]

Causes

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Melanocytic activation and melanocyte proliferation are the two primary processes of melanonychia.[3]Increasedmelaninproduction from a typical number of activatedmelanocytesin the nail matrix is referred to as melanocytotic activation. Increasedmelaninpigment results from a greater quantity ofmelanocyteswithin the nail matrix, which is known as melanocyte proliferation.[4]

Both pregnancy and racial melanonychia are physiological causes of longitudinal melanonychia. People with dark skin tones, includingAfrican Americans,Asians,Hispanics,and people from theMiddle East,often exhibit harmless longitudinal pigmented stripes.[5]

It is important to investigate the possibility ofonychotillomania,nail-biting,frictional trauma, and evencarpal tunnel syndromeif melanonychia is linked to anomalies of the nail plate or the periungual tissues.[6]A common cause of symmetric melanonychia that affects the great toe, the lateral and external portion of the fourth or fifth toenail, is recurrent trauma from overriding toes or poorly fitting shoes.[5][7]

Skin disorders suchonychomycosis,paronychia,psoriasis,lichen planus,amyloidosis,and chronicradiodermatitiscan causeinflammation,which can activatemelanocytesand result in the formation of a light-brown band. Melanonychia frequently develops after the inflammatory process has resolved.[5]Nonmelanocytic tumors such as subungual linearkeratosis,[8]verruca vulgaris,subungualfibrous histiocytoma,basal cell carcinoma,myxoidpseudocyst,[9]Bowen's disease,[10]andonychomatricomahave also been shown to induce melanocytic activation, which leads to longitudinal melanonychia.[11]

Systemic-related melenonychia sometimes presents as numerous bands including the fingernails and toenails. Interestingly, cutaneous and mucosal pigmentation are frequently seen in conjunction with melanonychia linked to nutritional problems,AIDS,andAddison's disease.[12]Alcaptonuria,hemosiderosis,hyperbilirubinemia,andporphyriahave all been linked to melanonychia.[5][9]

Medication (particularlychemotherapydrugs),phototherapy,radiation exposure fromX-rays,andelectron beam therapyare examples of iatrogenic causes of melanocytic activation.[13][14]

Melanonychia linked with syndromes, such asPeutz-Jeghers,Touraine, andLaugier-Hunziker,usually affects numerous digits and is accompanied by mucosal pigmented macules including the lips and oral cavity.[5]

The most frequent cause of brown-black coloration on nails ishematomas.It can be chronic (repeated, tiny trauma) or acute (after a single large trauma).[3]

Both dematiaceous and nondematiaceous fungi can induce fungal melanonychia; the most prevalent ones areTrichophyton rubrumandScytalidium dimidiatum,followed byAlternariaandExophiala.[15]

Mechanism

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Whilemelanocytesare found in the nail bed and matrix, most of them are dormant or quiescent.[3]Melanocyteactivation in response to trauma, infection, or inflammation starts the manufacture ofmelanin.Then,melanin-richmelanosomesare transported by dendrites to the developing matrix cells.[16]The nail plate becomes visibly pigmented when these matrix cells migrate in a distal direction and mature into nail plate onychocytes.[5]Melanonychia can also be caused by proliferation ofmelanocytesin the nail matrix, either with or without the formation of a nest (nevus)[3]

Diagnosis

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It is important to get a complete history, paying close attention to the beginning, development, and potential causes of melanonychia. All twenty nails, skin, and mucous membranes should be examined during the initial physical examination, bearing in mind all possible causes of brown-to-black nail coloration. It is best to rule out the possibility that an exogenous substance on top of or beneath the nail plate is the cause of the linear nail coloring.[17]

Using adermoscopycan help determine whether abiopsyis required. Because melanonychia is typically difficult to diagnose clinically, abiopsyis usually required to rule outmelanoma.[18]

Classification

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Longitudinal melanonychia or melanonychia striata is distinguished by a longitudinal brown-black/grey band that runs from the cuticle or nail matrix proximally to the nail plate's distal free edge. Diffuse or total melanonychia involves the entire nail palate. Transverse melanonychia is characterized by a transverse band across the nail plate's breadth.[3]

Treatment

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The underlying cause of melanonychia determines how to treat it. Regression of pigmentation may be brought on by the management of related systemic or locoregional diseases, the stopping of the offending medication, avoiding trauma, treating infections, or correcting nutritional inadequacies. Benign causes can be monitored and do not require treatment.[3]

Epidemiology

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About half of instances ofchromonychiaare caused by melanonychia. The most prevalent morphological pattern is longitudinal melanonychia.[19]

See also

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References

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  1. ^James, William; Berger, Timothy; Elston, Dirk (2005).Andrews' Diseases of the Skin: Clinical Dermatology.(10th ed.). Saunders.ISBN0-7216-2921-0.
  2. ^abFreedberg, et al. (2003).Fitzpatrick's Dermatology in General Medicine.(6th ed.). McGraw-Hill.ISBN0-07-138076-0.
  3. ^abcdefgSingal, Archana; Bisherwal, Kavita (2020)."Melanonychia: Etiology, Diagnosis, and Treatment".Indian Dermatology Online Journal.11(1). Medknow: 1–11.doi:10.4103/idoj.idoj_167_19.ISSN2229-5178.PMC7001389.PMID32055501.
  4. ^Tosti, Antonella; Baran, Robert; Piraccini, Bianca Maria; Cameli, Norma; Fanti, Pier Alessandro (1996). "Nail matrix nevi: A clinical and histopathologic study of twenty-two patients".Journal of the American Academy of Dermatology.34(5). Elsevier BV: 765–771.doi:10.1016/s0190-9622(96)90010-9.ISSN0190-9622.
  5. ^abcdefAndré, Josette; Lateur, Nadine (2006). "Pigmented Nail Disorders".Dermatologic Clinics.24(3). Elsevier BV: 329–339.doi:10.1016/j.det.2006.03.012.ISSN0733-8635.
  6. ^Aratari, Ester (1984-04-01). "Carpal Tunnel Syndrome Appearing With Prominent Skin Symptoms".Archives of Dermatology.120(4): 517.doi:10.1001/archderm.1984.01650400099023.ISSN0003-987X.PMID6703757.
  7. ^Baran, Robert (1987). "Frictional Longitudinal Melanonychia: A New Entity".Dermatology.174(6). S. Karger AG: 280–284.doi:10.1159/000249199.ISSN1018-8665.PMID3622879.
  8. ^Baran; Perrin (1999). "Linear melanonychia due to subungual keratosis of the nail bed: a report of two cases".British Journal of Dermatology.140(4). Oxford University Press (OUP): 730–733.doi:10.1046/j.1365-2133.1999.02780.x.ISSN0007-0963.
  9. ^abBaran, Robert; Kechi gian, Paul (1989). "Longitudinal melanonychia (melanonychia striata): Diagnosis and management".Journal of the American Academy of Dermatology.21(6). Elsevier BV: 1165–1175.doi:10.1016/s0190-9622(89)70324-8.ISSN0190-9622.PMID2685057.
  10. ^Sass, U.; André, J.; Stene, J.-J.; Noel, J.-Ch. (1998). "Longitudinal melanonychia revealing an intraepidermal carcinoma of the nail apparatus: Detection of integrated HPV-16 DNA".Journal of the American Academy of Dermatology.39(3). Elsevier BV: 490–493.doi:10.1016/s0190-9622(98)70331-7.ISSN0190-9622.PMID9738788.
  11. ^Fayol, R. Baran, C. Perrin, F. Labr, J. (2000-10-01)."Onychomatricoma with Misleading Features".Acta Dermato-Venereologica.80(5). Medical Journals Sweden AB: 370–372.doi:10.1080/000155500459330.ISSN0001-5555.PMID11200837.{{cite journal}}:CS1 maint: multiple names: authors list (link)
  12. ^Cribier, Bernard; Mena, Marcello Leiva; Rey, David; Partisani, Maria; Fabien, Vincent; Lang, Jean-Marie; Grosshans, Edouard (1998-10-01). "Nail Changes in Patients Infected With Human Immunodeficiency Virus".Archives of Dermatology.134(10). American Medical Association (AMA).doi:10.1001/archderm.134.10.1216.ISSN0003-987X.
  13. ^O'Branski, Erin E.; Ware, Russell E.; Prose, Neil S.; Kinney, Thomas R. (2001). "Skin and nail changes in children with sickle cell anemia receiving hydroxyurea therapy".Journal of the American Academy of Dermatology.44(5). Elsevier BV: 859–861.doi:10.1067/mjd.2001.113471.ISSN0190-9622.PMID11312437.
  14. ^Quinlan, Kathryn E.; Janiga, Jennifer J.; Baran, Robert; Lim, Henry W. (2005). "Transverse melanonychia secondary to total skin electron beam therapy: A report of 3 cases".Journal of the American Academy of Dermatology.53(2). Elsevier BV: S112–S114.doi:10.1016/j.jaad.2004.11.020.ISSN0190-9622.
  15. ^Finch, Justin; Arenas, Roberto; Baran, Robert (2012). "Fungal melanonychia".Journal of the American Academy of Dermatology.66(5). Elsevier BV: 830–841.doi:10.1016/j.jaad.2010.11.018.ISSN0190-9622.
  16. ^Perrin, Ch.; Michiels, J. F.; Pisani, A.; Ortonne, J. P. (1997). "Anatomic Distribution of Melanocytes in Normal Nail Unit".The American Journal of Dermatopathology.19(5). Ovid Technologies (Wolters Kluwer Health): 462–467.doi:10.1097/00000372-199710000-00005.ISSN0193-1091.
  17. ^Jefferson, Julie; Rich, Phoebe (2012)."Melanonychia".Dermatology Research and Practice.2012.Hindawi Limited: 1–8.doi:10.1155/2012/952186.ISSN1687-6105.PMC3390039.PMID22792094.
  18. ^Jellinek, Nathaniel (2007). "Nail matrix biopsy of longitudinal melanonychia: Diagnostic algorithm including the matrix shave biopsy".Journal of the American Academy of Dermatology.56(5). Elsevier BV: 803–810.doi:10.1016/j.jaad.2006.12.001.ISSN0190-9622.
  19. ^Bae, S; Lee, M; Lee, J (2018). "Distinct Patterns and Aetiology of Chromonychia".Acta Dermato Venereologica.98(1). Medical Journals Sweden AB: 108–113.doi:10.2340/00015555-2798.ISSN0001-5555.

Further reading

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  • Jin, Hyunju; Kim, Jeong-Min; Kim, Gun-Wook; Song, Margaret; Kim, Hoon-Soo; Ko, Hyun-Chang; Kim, Byung-Soo; Kim, Moon-Bum (2016). "Diagnostic criteria for and clinical review of melanonychia in Korean patients".Journal of the American Academy of Dermatology.74(6). Elsevier BV: 1121–1127.doi:10.1016/j.jaad.2015.12.039.ISSN0190-9622.PMID26830866.
  • Tosti, Antonella; Piraccini, Bianca Maria; de Farias, Débora Cadore (2009). "Dealing with Melanonychia".Seminars in Cutaneous Medicine and Surgery.28(1). Frontline Medical Communications, Inc.: 49–54.doi:10.1016/j.sder.2008.12.004.ISSN1085-5629.PMID19341943.
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