A teen-ager with linear atrophoderma of Moulin1. Unit of Dermatology Oasi Institute (IRCCS), Troina, Italy. firstname.lastname@example.org
Carmelo Schepis1, Rosaria Palazzo2, Maria Lentini3
Dermatology Online Journal 16 (2): 7
2. Unit of Dermatology Piemonte Hospital, Messina, Italy
3. Department of Human Pathology University of Messina, Italy
Linear atrophoderma, first described by Moulin, is an acquired unilateral dermatitis localized along the Blaschko lines. It affects children or adolescents of both genders, involving the trunk and the limbs. It is, presumably, a rare cutaneous form of mosaicism. The differential diagnosis of atrophoderma of Moulin involves congenital dermopathies along the Blaschko lines, atrophoderma of Pasini and Pierini, and linear scleroderma. We present here a peculiar case of linear atrophoderma affecting a teenager.
A 14-year-old boy was referred to us because of the onset and progression, over a period of a few months, of a wide asymptomatic pigmented plaque on the left side of the trunk. This brownish lesion, which seemed to be localized along the Blaschko lines (Figure 1), was slightly atrophic at palpation. No signs of hardening or inflammation were found.
Microscopic examination of the punch biopsy (Figure 2) showed a normal epidermis outlined by a hyperpigmented basal layer. In the upper dermis, dilated superficial vessels were visible. The mid and deep dermis were mildly edematous. The elastic fibers were normal, as demonstrated by the Weigert's resorcin-fuchsin method and the accessory structures preserved. A mild lymphocyte infiltrate was detectable around the small vessels.
The diagnosis of atrophoderma of Moulin was made in consideration of the clinical examination and the histopathological results.
In 1992, Moulin et al. described 5 patients presenting with hyperpigmented, depressed plaques occurring along the Blaschko lines . The condition was later named “Linear atrophoderma of Moulin” (LAM) . No inflammatory events seem to precede the onset of LAM, nor does it evolve in sclerosis. Linear atrophoderma of Moulin is usually localized along Blaschko lines, is unilateral, affects children or adolescents of both genders, and involves trunk and limbs . It is, presumably, a cutaneous form genetic mosaicism. Some authors suggested an inflammatory phase might precede the atrophic and pigmented phase of LAM ; thus, they assumed the presence of both inflammatory and non-inflammatory variants of the disease.
The differential diagnosis of LAM  involves congenital dermopathies following Blaschko lines, atrophoderma of Pasini and Pierini (APP), and linear scleroderma.
Dermopathies presenting with patterns along Blaschko lines and with macular and hyperpigmented morphology, such as Linear and Whorled Nevoid Hypermelanosis, do not show atrophy  and are usually congenital or manifest during childhood. Epidermal nevi, such as the papular form, manifest in early childhood or at birth. Lichen striatus, which is, on the contrary, an acquired disease, is also papular and is easily distinguishable clinically from LAM. Focal dermal hypoplasia, the presents with atrophic and hyperchromic lesions, occurs along Blaschko lines, but is already present at birth and often exhibits distinctive extracutaneous anomalies (skeletal, ocular) characterizing the Goltz Syndrome phenotype . Linear scleroderma can be considered clinically, although it is not clear whether it occurs along Blaschko lines, but can be distinguished histologically. Atrophoderma of Pasini and Pierini is a dermopathy very similar to LAM but it does not follow Blaschko lines. It is possible that LAM is only a variant of APP, localized along Blaschko lines. However, the correlations between these two entities do not seem to have been clarified yet .
The etiology of LAM is unclear. The idea of a lethal gene surviving by mosaicism , which can be found in conditions such as Proteus syndrome or Schimmelpenning syndrome, has not been evaluated.
The pathogenesis of acquired dermatitis localizing along Blaschko lines, such as Lichen striatus-Blaschkitis, linear psoriasis  and LAM, has not yet been identified. So far, the hypothesis made by Happle  that transposable elements may cause similar skin lesions seems to be the most plausible. However, this epigenetic mechanism is still an unproven hypothesis in man.
There is no proven effective treatment for LAM. As lesions develop over a limited period of time and then stabilize, it is difficult to assess the efficacy of any intervention. Topical steroids have been reported to be ineffective.
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