Linear atrophoderma of Moulin

ARTICLE

Linear atrophoderma of Moulin is a rare entity first described by Moulin in 1992 [1]. It is characterized by asymptomatic hyperpigmented atrophic band-like lesions localized mostly on the trunk and following the lines of Blaschko. Baumann et al. [2] suggested the term "linear atrophoderma of Moulin" for these band-like scleroderma-like skin lesions that do not show a preceding inflammation or induration. They categorized this disease as belonging to the group of acquired linear dermatoses following Blaschko's lines. The skin lesions usually first appear during childhood and adolescence and subsequently remain unchanged.

To date, 9 cases of linear atrophoderma of Moulin have been reported [1-5]. In addition, two cases reported under another diagnosis can today be assigned to this disorder [6-8]. We report a further typical case of this so far poorly-known clinical entity.

Case report

In January 1998, a 17-year-old woman was referred to the Department of Dermatology, Klinikum Kassel, Germany, with a 3-year history of an asymptomatic linear skin lesion affecting the right side of her trunk. The lesion first appeared on the back and gradually extended to the anterior midline. After a short period of rapid enlargement, the skin disorder remained unchanged.

Physical examination showed a hyperpigmented and atrophic band-like skin lesion measuring 3-5 cm in breadth on the right side of the trunk (Fig. 1), and another one on the right buttock. Both streaks started a few cm from the posterior midline and followed Blaschko's lines. The skin lesions had a normal texture and showed no signs of inflammation such as lilac ring or erythema, and no induration or sclerosis.

Laboratory findings including a test for Borrelia burgdorferi antibodies were normal except for elevated serum IgE (197 kU/l). Antinuclear antibodies (ANA) and anti-Scl70-antibodies were negative. Chest X-ray and ultrasound examination of the abdomen gave normal results.

A skin biopsy was taken from the marginal zone of the skin lesion. Histopathological examination showed a moderate diffuse hyperpigmentation within the lower part of the epidermis and a focal vacuolar degeneration of the basal layer (Fig. 2). In these areas hyalin eosinophilic units, reminiscent of Civatte bodies were found. In the dermis, melanin-laden macrophages and a few perivascular lymphocytes were present. The collagen bundles appeared to be slightly thickened, whereas the elastic fibres were unchanged (Fig. 3).

Penicillin G was administered intravenously over a period of 14 days in a dosage of 10 x 10⁶ IU twice daily. This treatment was repeated after 3 and 9 months. No improvement was noted.

Discussion

Linear atrophoderma as described by Moulin et al. in 1992 [1] is an acquired disorder characterized by the rather sudden appearance of hyperpigmented atrophic band-like skin lesions in otherwise healthy children or young adults. The lesions are localized on the trunk or the limbs. They start a few centimeters from the posterior midline and follow Blaschko's lines. There is no inflammation, induration, scleroderma or epidermal atrophy. Usually the lesions remain stable in localisation, color and size. There are no subjective symptoms. No other abnormalities have been described to be associated with this skin disorder [1-5].

The individual skin lesions of linear atrophoderma of Moulin closely resemble those of atrophodermia idiopathica of the Pasini and Pierini type (AIPP) which however, never follow Blaschko's lines. Retrospectively, at least two cases as described in the literature can be assigned to linear atrophoderma of Moulin [6-8]. It is so far a controversial issue whether linear atrophoderma of Moulin represents a distinct entity or a clinical variant of AIPP [2]. AIPP itself has been discussed controversially as either a separate disorder or a variant of circumscribed scleroderma [9-18].

In skin biopsies of linear atrophoderma of Moulin, an irregular and moderate hyperpigmentation of the lower part of the epidermis is found. The dermis is unaffected except for the inconstant presence of a slight perivascular lymphocytic infiltrate. Occasionally, a collagen sclerosis can be observed [4]. The presence of hyalin eosinophilic units within the basal epidermal layers, reminiscent of civatte bodies as known from lichen planus, is an occasional and non-specific finding (Fig. 2).

Moulin et al. did not detect abnormal laboratory findings [1]. Antinuclear antibodies have been reported in one case of linear atrophoderma of Moulin only [2], but the significance of this finding is uncertain. Similarly, the implication of laboratory abnormalities - especially ANA - in circumscribed scleroderma and AIPP, is a controversial issue. In our case, the results of laboratory analysis were normal except for a slight elevation of serum IgE which should be taken as a coincidental finding.

Linear atrophoderma Moulin should be discriminated from other disorders that show similar configuration, atrophy and hyperpigmentation. AIPP is a rare form of dermal atrophy of unclear cause. This disease is characterized by the appearance of circumscribed, reddish-brown atrophic lesions without preceding inflammation on otherwise normal skin. The lesions are observed in adults as well as children and are otherwise asymptomatic. However, these lesions tend to show signs of changes such as confluence and enlargement [14, 17]. Several authors reported subsequent induration or sclerosis of the lesions [17, 18]. Most patients with AIPP show a bilateral symmetric distribution, usually orientated along the skin cleavage lines [12, 16], but a unilateral involvement has likewise been reported [9]. However, AIPP does not follow the pattern of Blaschko's lines. On the other hand, a large variety of skin diseases follow Blaschko's lines, e.g., incontinentia pigmenti, Goltz syndrome, lichen striatus and pigmentary mosaicism of the Ito type [19-23]. In our patient, the initial clinical diagnosis was linear scleroderma. However, the impressive configuration of the skin lesions and the absence of inflammation, sclerosis or induration led to a diagnosis of linear atrophoderma of Moulin.

The etiology and pathogenesis of the disorder remains unknown. All reported cases were so far sporadic. The disorder may illustrate a clonal proliferation of mutant cells during embryogenesis [1, 2, 23]. This clone of mesodermal origin may be characterized by an aberrant pattern of tissue antigens giving rise to a selective autoimmune attack later in life. If this concept holds true, linear atrophoderma of Moulin would be an additional argument against the hypothesis that the lines of Blaschko are exclusively of ectodermal origin [24].

Topical treatments with steroids or heparin showed no effect in linear atrophoderma of Moulin [2]. Igarza et al. treated a 16-year-old girl by oral potassium aminobenzoate and described an "early stabilization of the skin lesions" [4]. Treatment with UV-light has shown improvement in some patients whereas aggravation was seen in others [1]. Wollenberg et al. [3] documented no benefit from intravenous penicillin. Our patient reported a slight decrease of hyperpigmentation, but we were unable to substantiate this effect. In circumscribed scleroderma the antiinfectious effect of penicillin and the influence on the collagen metabolism after conversion of penicillin to D-penicillamin have been discussed [25, 26]. In conclusion, there is so far no well-etablished therapeutic approach to linear atrophoderma of Moulin.

Article accepted on 20/7/00

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