Idiopathic guttate hypomelanosis is a common dermatosis of unknown etiology, characterized by small white spots on sun-exposed areas of the upper and lower extremities. ICD-10 code: L81.9
Idiopathic guttate hypomelanosis is more common in fair-skinned individuals of middle and older age, with a higher incidence in women.
The exact cause of its development is unknown. There is a higher prevalence among family members, suggesting a genetic predisposition. One study suggests a possible association with HLA-DQ3 and the development of idiopathic guttate hypomelanosis.
Patient concerns are mainly related to the appearance of the lesions and their potential for malignancy. Actinic damage is thought to be the main cause of the condition, but senile degeneration may also play a role.This condition typically begins in adolescence, often affecting the shins first, then spreading to the forearms, shoulders, and thighs, rarely the neck. Face is never involved. The spots are white and hypopigmented, with a diameter of 2-5 mm in diameter, with regular borders. They may have smooth or slightly sclerotic scaling. The spots are scattered on sun-exposed areas of the upper and lower extremities.
Patients may also show signs of sun-induced skin aging, including atrophy, lentigo spots, and xerosis on the same areas. Lesions remain stable in size and fixed in location. The number of spots tends to increase with the patient's age.- Vitiligo (tends to have a symmetrical distribution, with small spots developing into larger ones).
- Pityriasis versicolor (prefers the upper part of the trunk, potassium hydroxide test result is positive).
- Chemical-induced hypomelanosis due to exposure to depigmenting agents related to the patient's profession (mainly affects the hands and forearms).
- Tuberous sclerosis (manifests in childhood and adolescence, along with associated neurological signs).
- Pityriasis alba (possibly represents post-inflammatory hypopigmentation, tends to resolve over several years).
- Bier spots - angiopathic leukoderma (disappear upon rubbing).
- Stucco keratosis
Reassuring patients about their condition is often enough for most of them. White spots can be camouflaged with cosmetic cover-ups such as "Covermark" or "DermaBlend." Self-tanning creams containing dihydroxyacetone can darken the spots, but the appearance remains speckled and unsatisfactory from a cosmetic perspective.
Light cryotherapy with liquid nitrogen can partially remove the lesions, but the potential for worsening is present. Intralesional injection of triamcinolone (2.5 mg/mL) may partially induce repigmentation of the spots, but there is a risk of atrophy.
Wearing sun-protective clothing is recommended as sunscreens are less effective.