Pediatrics is seasonal, and summer is the season for check-ups and rashes which include areas of hyperpigmentation, unusual blotches of skin that tan darker than the surrounding skin. These areas typically appear on the face, arms or legs and have a variety of causes.
Melanocytes
Pigmentation in the skin is controlled by a specialized cell, the melanocyte, which is present in the epidermis and hair follicles. Ultraviolet light stimulates melanocytes to produce a pigment, melanin, and deposit it in nearby skin cells, keratinocytes. Localized areas of darker pigmentation may be due to an aggregation of melanocytes, or variations in melanin production or distribution. The most common sun-related hyperpigmentation is a freckle, areas of increased melanin pigment that often appear in preschool-aged children.
Post-Inflammatory Changes
The most common abnormal hyperpigmentation is due to post-inflammatory pigment changes. Any area of inflammation, from mild eczema to infections to abrasions and lacerations, will alter the pigmentation of skin. It is more noticeable with sun exposure and may result in either hyperpigmentation or hypopigmentation, a decrease in skin pigment. If the inflammation is not ongoing, such as eczema, the difference in pigmentation may last for six months to a year.
Other Causes
Some medications can cause a sun-sensitive reaction. Among these is the tetracycline family of antibiotics, commonly used to treat acne, and bleomycin, a chemotherapy drug, used in some childhood cancers. Melasma is a condition thought to be related to estrogen which causes dark blotchy areas of the face and neck. Occurrence begins during the teenage years, and it occurs mostly in women of Latin, Indian, Asian and Mediterranean descent, frequently during pregnancy.
Concerns
Some areas of hyperpigmentation are of concern. The most common example is a nevus, commonly called a "mole." Nevi appear throughout childhood, more so through adolescence, and more slowly in early adulthood, after which they may begin to fade. The number of nevi present on your body is directly related to your risk of developing a malignant melanoma, which accounts for 1 to 3 percent of all pediatric malignancies and is the second most common cancer in young adults, ages 15 to 29 years, reports the "Nelson Textbook of Pediatrics."
Prevention
With sun-related hyperpigmentations and melanomas, prevention is the key. Unfortunately, sunscreens are widely misunderstood and under used, as most sunscreens block UVB rays which cause burning, but do not affect UVA rays, which stimulate melanocytes and contribute to melanomas. Only broad spectrum sunscreens, such as zinc oxide and titanium oxide, effectively block UVA rays, but the best prevention is avoiding peak sunlight hours and wearing a shirt and hat.
References
- American Academy of Dermatology: Melanocytes
- Medscape: Disorders of Pigmentation Slideshow
- "Nelson Textbook of Pediatrics"; RE Behrman, MD, RM Kliegman, MD, and HB Jenson, MD; 2000
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