Dr Nick Lowe advises on acquired pigment lesions – when to treat and when to refer

Pigment problems of the skin are many and varied. The most important advice for practitioners is to be certain of the diagnosis of the pigment problem or lesion before embarking on treatment.

MECHANISMS OF PIGMENTATION

All skin phototypes have the same skin frequency of melanocytes i.e. one melanocyte to every 10 keratinocytes. It is the ability of individual melanocytes to induce new melanin pigment in packaged melanosomes that varies from skin type and between individuals. For example, redheads do not produce the most common type of melanin that other skin types possess. They produce phaeomelanin which, unfortunately, offers no ultraviolet protection.

Increased pigment production in the main is induced by exposure to ultraviolet sunlight, but several other factors can influence the degree of pigmentation. These include hormones (pregnancy and hormonal contraceptives) and medicines, such as amiodarone. In addition, there are a range of congenital pigment abnormalities that this article will not address.

Solar lentigo

Frequent pigment lesions are solar lentigines which only appear on sun-exposed skin. Benign lentigines must be differentiated by their appearances from lentigo maligna. Other differential diagnoses include face and neck melasma, drug-induced melanosis, post-inflammatory hyperpigmentation from skin diseases (e.g. acne, eczema, lichen planus) and other inflammatory skin diseases.

Solar lentigines are likely to recur if the patient does not apply daily broad-spectrum sunscreen and prescription strength hydroquinone 4-5% cream. A variety of other non-prescription product ingredients and options are available that may give minimal or modest degrees of skin lightening, including liquorice extract, niacinamide, azelaic acid, low strength non-prescription retinoids and soy extract.

Options for clinic treatments of benign lentigo include pigment-specific lasers, such as the Ruby or Alexandrite lasers and non-pigment specific lasers (e.g. different wavelengths of fractional lasers such as 1550nm and 927nm). Intense Pulse Light (IPL) using appropriate filters is useful for treating multiple lentigo, however, care needs to be taken with IPL wavelength and energy selection in skin phototypes III and darker.

Pigmented naevi

Most dermatologists agree that before pigmented naevi are treated it is essential that they are confirmed to be benign. This may involve a skin biopsy after examination by dermoscopy. If the practitioner is satisfied with the benign nature of the pigment naevus appropriate laser treatment can be considered. If surgical removal is not required, appropriate lasers for benign pigmented naevi include long-pulsed Alexandrite lasers, which in my experience give long-term improvement compared to Q-switched or pico lasers. It is important to inform the patients that both lentigo and benign pigment nevi may recur after laser treatment and require further treatment sessions for maximum improvement.

Pigmented naevi must be accurately diagnosed as benign prior to treatment. Any irregularity of pigment outlines other clinical features and the patient ideally should be referred for dermatologic opinion.

The risks of treating a pigmented lesion where the diagnosis is a malignant lesion cannot be overstated. This can delay and confuse correct diagnosis and prompt treatment of a melanoma or pigmented basal cell cancer.

Melasma

Melasma is a frequent problem which usually requires combined treatments with prescription topical products as well as advice for prevention to reduce recurrence after clinic treatment.

A variety of melasma treatments are often used in combination to obtain optimum lightening.

Dr Nick Lowe is a consultant dermatologist at Cranley Clinic, London, and clinical professor of Dermatology at UCLA School of Medicine, Los Angeles. Dr Lowe is a Fellow of numerous societies and colleges, including the Royal College of Physicians, American Academy of Dermatology and American Society of Laser Medicine and Surgery. He is past president of both the Pacific Dermatology Association and the Cosmetic Dermatology Group of the British Association of Dermatology. He has authored more than 450 clinical and research publications as well as 15 scientific and five educational books for the public.