Idiopathic guttate hypomelanosis L81.5

Costa 1951; Cummings and Cottel 1966

Harmless, only cosmetically disturbing, disseminated, white-grey, confetti-like, slightly keratotic, porcelain-like spots or flat papules on UV-exposed lower legs and forearms. Affected are mainly UV-exposed, fair-skinned persons. The combination with xerosis of the skin is frequent (Brown F et al. 2021).

Epidemiological data are not available because the disease is often not noticed. However, it can be assumed that the skin changes occur frequently. According to estimates of various authors, the prevalence in >70 year olds is > 80%.

Affected are mainly light-damaged persons in middle and higher age. Skin changes increase with increasing age while maintaining the same lifestyle (actinic stress).

Symptomless, solitary, but mostly disseminated, white, slightly sunken spots (or plaques) of varying size (0.2-0.6 cm in diameter). Their surface appears parchment-like atrophic. The changes are particularly prominent in tanned skin.

Atrophically flattened surface epithelium that keratinizes orthokeratotic or orthohyperkeratotic over a stratum granulosum.

Stratum basale: Reduction of the melanin granules in the lesional epidermis in prominent melanocytes. The dermis shows no inflammatory reaction.

An enlargement and rounding (retraction of the dendrites) of the melanocytes is detectable. Melanin is accumulated in melanocytes. This probably leads to a senescence of the melanocytes. Apparently the accumulation of melanin in lesional melanocytes is due to an acquired transfer disorder of melanosomes to keratinocytes(Rani S et al. 2018).

Circumscript scleroderma (confetti-like form): Localization would be atypical. Histology is diagnostic.

Lichen sclerosus (disseminated form): Localization would be atypical. Histology is diagnostic.

Vitiligo: the skin lesions of vitiligo are rarely extensor and limited to the extremities.

Note: Ultimately, the distribution pattern combined with the age of the affected person (>50 years) and an increased cumulative sun exposure leads to the diagnosis. A histologic diagnosis is usually not necessary.

1. Arrunategui A et al (2002) HLA-DQ3 is associated with idiopathic guttate hypomelanosis, whereas HLA-DR8 is not, in a group of renal transplant patients. Int J Dermatol 41: 744-747
2. Böhm M (2015) Differential diagnosis of hypomelanosis. Dermatol 66: 945-958
3. Brown F et al (2021) Idiopathic guttate hypomelanosis. 2020 Sep 20. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. PMID: 29489254.
4. Cummings KI et al (1966) Idiopathic guttate hypomelanosis. Arch Dermatol 93: 184-186
5. Lal K et al (2015) What is your diagnosis? idiopathic guttate hypomelanosis. Cutis96:156
6. Min-Kyung Shin et al (2011) Clinical features of idiopathic guttate hypomelanosis in 646 sunjects and association with other aspects of photoaging. Int J Dermatol 50: 798-805
7. Pagnoni A et al. (1999) Hypopigmented macules of photodamaged skin and their treatment with topical tretinoin. Acta Derm Venereol 79: 305-310
8. Rani S et al (2018) Melanocyte abnormalities and senescence in the pathogenesis of idiopathic guttate hypomelanosis.Int J Dermatol 57:559-565.
9. Wallace ML et al (1998) Numbers and differentiation status of melanocytes in idiopathic guttate hypomelanosis. J Cutan Pathol 25: 375-379