Melanonychia Striata Longitudinalis (MSL) is also referred to as pigmented bands. Melanonychia is a medical term used to describe black or brownish pigmentation involving the nail plate. MSL is a band of pigmentation that runs along the length-wise portion of the nail, along the nail bed. Multiple nails may be involved.
It can present in individuals of all ages, including children and affects both sexes equally. It occurs more commonly in patients with skin of color, especially in those with darker complexions. Nearly all Afro-Caribbean people will develop pigmented bands by the age of 50, and interestingly, up to 20% of Japanese people will also develop MSL. Melanonychia has also been associated with genetic disorders, injury, nutritional deficiency, endocrine disease, connective tissue diseases, inflammatory skin disease, local tumors and nail infections…although most of these cases do not produce the linear banding observed in MSL and involve most, if not all, of the nail.
ETIOLOGY: The nail plate is translucent and made of keratin. Melanocytes usually lie dormant in the proximal nail matrix where the nail is produced. In MSL melanin is deposited into the growing nail when melanocytes are activated.
TREATMENT: No treatment is indicated. The major concern in the differential diagnosis is melanoma which can involve the nail. Dermoscopy can help differentiate pigmented bands and melanoma. Melanoma usually progresses and leaches pigment into surrounding tissue and this is called Hutchinson’s sign. To exclude this diagnosis a biopsy may need to be performed and often results in a permanent nail defect because the base of the nail is the site for biopsy. Once again, this blog is not meant to substitute for a clinic visit and if you have a pigmented band that is changing, getting darker or widening, you need to be evaluated by a dermatologist to be sure that it is not a subungual melanoma. To read more about MSL click HERE, HERE and HERE.