Black streaks on nails


Black streaks on nails: what might be hiding underneath that beautiful nail varnish coat?

Originated in China in 3000BC as a sign of wealth and prosperity, nail polish has globalised to become a quick and simple, relatively inexpensive treatment that adds that touch of glamour and finesse we all strive for. It is unknown what percentage of women regularly use nail polish, but it has been estimated that more than half of the women worldwide use it at least once a month. In fact, manipedis have become an integral part of so many womens’ lives that their nails are almost never without polish.

However, are you aware that these perfectly pruned, buffed and polished nails could be masking vital clues to your state of health? Yes, those funny spots, streaks and indentations, which we try to mask with nail varnish can all signal important underlying skin or medical problems. The most important sign not to ignore is a black streak down the nail. This appears as a brown or black strip usually arranged along the length of the nail (known as longitudinal melanonychia - see image below). Longitudinal melanonychia affecting multiple nails can be totally normal in dark skinned individuals. It may also appear in pregnancy or be due to underlying medical disorders such as thyroid disease, nutritional deficiencies and chemotherapy or other medications. Longitudinal melanonychia affecting a single nail could be due to trauma, infection or harmless moles or pigment spots of the nail. However, the most serious cause of longitudinal melanonychia (particularly when a single nail is involved) is melanoma skin cancer of the nail. 

Nail melanoma affects men and women equally. Dark skinned individuals are also at risk of developing melanomas at this site as, unlike their skin, their nail bed is pale and still prone to the damaging effects of ultraviolet light. In fact the nail is one of the commonest sites to be affected by melanoma in darker skin types. Any new or pre-existing dark stripe that has recently changed in appearance warrants concern, including alteration of colour, pattern or size of the band. In this situation you should arrange to see your Dermatologist urgently for further investigation, which may involve a small surgical procedure to sample (biopsy) the nail bed.

The ‘ABCDEF’ signs may be used by your Dermatologist to assess the likelihood of the dark stripe being due to a melanoma

  • A = Age: Nail melanomas are more common in the 50-70 year age group

  • B = Breadth: The width of the dark band being >3mm with uneven borders

  • C = Change: Look for change in the appearance and pattern of the dark band

  • D = Digit: Thumbnails are more frequently affected, followed by big toenails

  • E = Extension: ‘Spill-over’ of pigment onto the cuticle and or nail fold (Hutchinson’s sign) may be present in nail melanomas

  • F = Family history of skin cancers, particularly melanoma

As with all cancers, the earlier it is treated, the better the outcome. So, whilst I too am a huge fan of nail varnish, my advice to you is simple: spending just a few minutes in between manipedis inspecting your nails thoroughly may seem trivial, but could potentially be life saving.

Christina Vlachou