Melanonychia

Melanonychia
Causes	Racial, skin cancer, infection, medications, lichen planus[1]
Risk factors	Dark skin[2]
Diagnostic method	Appearance, biopsy[2]
Differential diagnosis	Subungal melanoma
Frequency	Common,[3] males=females[1]

Melanonychia, a type of chromonychia, describes a black or brown discoloration of finger or toenails.^[3][4] It typically appears as long vertical bands, but can be transverse, running horizontally across the nail, or involve the whole nail.^[2] The bands can vary in width and number.^[3] When a single longitudinal melanonychia dark band or mark suddenly appears in a single previously normal nail, a diagnosis of skin cancer needs ruling out.^[5]

Melanonychia is a type of discoloration in the nail.^[4] It can be normal or be associated with cancer or direct injury.^[1] It can occur in some inherited disorders such as Peutz-Jeghers syndrome, endocrine disease such as Addison's disease, skin diseases such as lichen planus and acanthosis nigricans, and nutritional deficiency such as vitamin B12 deficiency.^[2] It may be associated with some treatments such as PUVA therapy, ionizing radiation, and chemotherapy.^[2] Medications that cause discoloration of nails include antimalarials, minocycline, and antivirals such as zidovudine.^[2] Fungal nail infection can present with melanonychia.^[2]

Diagnosis is usually by appearance.^[2] A biopsy is required if there is a single new band in one nail, and may be required if the band is triangular where it is narrower near the nail fold, if the band border is blurred, if the discoloration is not uniform, if the band is wider than 6mm, or there is pigment of the periungal skin.^[2] It may appear similar to subungal melanoma.^[6]

It is common, occurs in all ages, and males and females are affected equally.^[1] Between 77 and 96% of black people and 11% of Asian people have longitudinal melanonychia.^[2]

Definition and signs

Melanonychia is the term used to describe the black or brown discoloration of finger or toenails.^[3] It typically appears as longitudinal bands, but can be transverse or involve the whole nail.^[2]

• 
  Melanonychia (longitudinal)
• 
  Melanonychia (transverse)
• 
  Melanonychia (whole nail)

Causes

Melanonychia can be normal or be associated with cancer or direct injury.^[1] It can occur in some inherited disorders such as Peutz-Jeghers syndrome, endocrine disease such as Addison's disease, skin diseases such as lichen planus and acanthosis nigricans, and nutritional deficiency such as vitamin B12 deficiency.^[2] It may be associated with some treatments such as PUVA therapy, ionizing radiation, and chemotherapy.^[2] Medications that cause discoloration of nails include antimalarials, minocycline, and antivirals such as zidovudine.^[2] Fungal nail infection can present with melanonychia.^[2] It can also occur in pregnancy and graft-vs-host disease.^[5]

Depending on the cause, the number and width of the coloured bands vary.^[3] Drug exposure, skin diseases, and racial pigmentation characteristically involve multiple nails, and cancer tends to present with discolouration in one nail.^[3]

Diagnosis

Diagnosis is usually by appearance.^[2] A biopsy is required to rule out skin cancer if a single longitudinal melanonychia dark band or mark suddenly appears in a single previously normal nail, if there is a personal or family history of melanoma, or if the band darkens, grows wider, becomes raised with blurry borders, and if the nail folds exhibits pigment.^[5]

Epidemiology

It is common, occurs in all ages, and males and females are affected equally.^[1] Between 77 and 96% of black people and 11% of Asian people have longitudinal melanonychia.^[2] Almost all Afro-Caribbean people will have some brownish nail discolouration by age 50.^[1]

See also

• List of nail conditions

References