Also known as Becker’s melanosis
What is a Becker’s naevus?
Becker’s naevus is a birthmark that appears in adolescence or the twenties as a flat brown discolouration in which darker thicker hairs may later grow. It is usually located on the shoulder, chest or back. It occurs most commonly in males.
What causes Becker’s naevus?
Becker’s naevus is a developmental abnormality in which there is an overgrowth of some tissue types. The surface skin is thickened, the pigment producing cells produce more melanin and there may be associated an increased number of muscle fibres in the dermis which make it feel thicker than normal skin. There are no reports of malignant change in these tissues.
Becker’s naevus is not an inherited disorder and is not passed on to the next generation.
What does Becker’s naevus look like?
Becker’s naevus starts as a large area of more pigmented, but otherwise normal skin. It is most commonly seen on the trunk (mostly on the shoulder or chest and less commonly on the legs or arms. Later there is an increased growth of hair that slowly becomes thicker and darker. Sometimes there is no hair growth. Sometimes the pigmentation change is absent and only the hairs are seen. The skin may feel thicker if the deeper skin muscle fibres are present in greater than normal amounts.
Becker’s naevus occurs more commonly in males (incidence of males to females is 6:1).
How is Becker’s naevus diagnosed?
The diagnosis is usually made by the doctor taking a history of its development and examining the lesion.
Sometimes a biopsy is required to differentiate a Becker’s naevus from a café au lait macule which is usually present at birth or develops in the first year of life.
There is a rare condition called Becker’s naevus syndrome in which a Becker’s naevus occurs in conjunction with a number of other abnormalities of the skin and bones. Becker’s naevus syndrome is more common in women. The other abnormalities are detected during a physical examination by the doctor who uses other investigations to confirm the diagnosis.
How is Becker’s naevus treated?
The appearance of a Becker’s naevus may be improved but it cannot be eradicated.
The lesions are usually too large to be removed surgically.
The pigmentation may be improved by the use of camouflage make-up. Laser treatments to reduce the pigmentation have not been very successful and recurrence of the pigmentation is common.
The excess hair may be reduced or eradicated with laser treatment. Multiple treatments are needed. Repeat treatment every two or three years may be required.
The thickened skin is extremely difficult to treat. Some laser treatments have been tried but have not been very successful.
This information has been written by Dr Davin Lim
Updated 18 August 2015