Dermatology Online Journal

Ashy dermatosis, or "Tyndall-effect" dermatosis
Angel Fernandez-Flores MD PhD¹, Manuel G Montero MD²
Dermatology Online Journal 12 (4): 14

Services of Anatomic Pathology¹ and Dermatology², Clinica Ponferrada, Leon, Spain. gpyauflowerlion@terra.es

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Abstract

A 59-year-old man with ashy dermatosis is presented; the classification and diagnosis of this disease is discussed. Ashy dermatosis presents two main clinical aspects: the ashy-color maculae, and the involvement mainly in darker-skinned patients often from Latin America and Asia. The blue-grey color can be explained by the Tyndall effect because of the melanin found in the dermis. Bluish dermal melanocytoses are also more common in these same racial and ethnic groups. Perhaps the particular size and distribution of melanosomes in these groups predisposes them to development of ashy dermatosis.

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Introduction

Ashy dermatosis is a controversial entity that has received many names in the literature. It has sometimes been associated with other diseases, and sometimes considered a variant of lichen planus (LP) [1, 2].

Some authors suggest that the condition is no more than a post-inflammatory pigmentary change in dark-skinned people [3]. However, although the disease is mainly described in patients with dark skin, it has been occasionally described in light-skinned patients. The bluish-grey aspect of the lesions, which led to the name ashy dermatosis, is the result of the Tyndall effect. It may be that certain characteristics of melanosome size and distribution predispose to the development of this pigmentary anomaly. We recently reviewed these concepts when evaluating a case of ashy dermatosis in a 59-year-old man.

Clinical synopsis

A 59-year-old man presented with several pruriginous, hyperpigmented macules in both axillae; they appeared 2 weeks prior as reddish lesions. Skin examination revealed the presence of multiple bluish-grey maculae in both axillae, in a symmetrical distribution; the largest was 2 cm in diameter. The surface of the lesions was shiny. The rest of the examination, as well as laboratory tests (CBC, liver and kidney function tests) were normal. The patient was taking no drugs. His skin was Fitzpatrick type IV.

At first, his condition was assumed to be post-inflammatory hyperpigmentation, possibly secondary to lichen planus; topical corticosteroid therapy was initiated. The patient returned 4 weeks later with larger macules (up to several cm) with the same color and appearance as the first ones. The macules were distributed on the neck (Fig. 1), both axillae, the cheeks, the eyelids, and the dorsal aspect of the upper trunk (Fig. 2).

Figure 1	Figure 2
Figure 1: Bluish-grey maculae in the neck and the cheeks of the patient Figure 2: Several grey maculae at the back of the patient.

Figure 3	Figure 4
Figure 3: Superficial perivascular dermatitis. Even at this magnification, dermal melanophages stand out Figure 4: A closer view of the dermal melanophages

Figure 5
Figure 5: Vacuolar degeneration of the basal layer of the epidermis

One of the truncal lesions was biopsied. The histopathological study showed superficial perivascular dermatitis, with a mild perivascular lymphocytic infiltrate in the papillary dermis and atrophy of the suprajacent epidermis (Fig. 3).

Many melanophages were present in the papillary dermis (Fig. 4). Histochemical study for iron was negative. Vacuolar degeneration of the basal cells was found (Fig. 5), with evidence of some Civatte-bodies.

Discussion

Ashy dermatosis has been a very controversial term in the literature. The term was coined owing to the description in 1957 of some patients who were called los cenicientos [4], which in Spanish means the ashen ones.

From its description, it was clear that the disease showed a tendency to appear mainly in dark-skinned people and this was supported later in the literature [4, 5, 6, 7]; cases were also described in Asians [8, 9]. Nevertheless, the condition is described occasionally in patients of other racial-ethnic backgrounds [4, 8, 10, 11, 12].

Ashy dermatosis has not always been recognized as an independent entity, and many have included it or related it to other cutaneous inflammatory diseases. The confusion about this diagnosis is confirmed by the many different names by which the disease is also known, such as erythema dyschromicum perstans [4], cinderella dermatosis [8], lichen planus pigmentosus [1], erythema cinitensis perstans [13], erythema chronicum figuratum melanodermicum, invisible pigmented lichen planus [8], or pigmentation maculosa multiplex idiopática [14]. Perhaps the relationship most frequently mentioned in literature, is with lichen planus [15, 16]. In fact, some clinicians consider ashy dermatosis to be nothing but a variant of LP [1, 2].

Others have alleged that ashy dermatosis presents clear clinical characteristics that distinguish it from other diseases [4, 5], although histopathological findings are not considered specific even by those who defend it as a clinical entity [4]. Even some of the clinical characteristics, which are helpful in distinguishing between LP and ashy dermatosis, are somewhat variable in the literature. For instance, ashy dermatosis is supposed to have a symmetrical presentation, but cases with a unilateral distribution are also described [2]. In addition, although pruritus helps to distinguish LP from ashy dermatosis, pruriginous cases of ashy dermatosis are reported [17].

Many authors point out that ashy dermatosis could be just the outcome of prolonged damage to the basal cell layer in many conditions with a lichenoid pattern [4, 18], essentially just a type of post-inflammatory hyperpigmentation stage [3]. The hyperpigmentation in ashy dermatosis is attributed to the presence of dermal melanophages [4, 5, 8, 11, 12, 17].

Two characteristics of ashy dermatosis stand out though, as interesting. One is the bluish-grey color of the lesions, which is not present in other post-inflammatory conditions; the other is the preference for dark-skinned patients in certain ethnic groups. Curiously, these are the same populations in which some other blue-grey lesions are described, such as Ota's and Ito's nevi (in Asians [19], Hispanics, Blacks and Native Americans) and Mongolian spot (Asian or African) [20].

It is a very well known fact how racial differences in skin-color are mainly the result of the number, size, distribution, degree of melanization, and the rate of degradation of melanosomes within keratinocytes [21]. Melanosomes in Caucasian individuals are distributed as membrane-bound clusters; melanosomes in African-American individuals are larger and are distributed individually [22]. In Asians, the distribution is a combination of individual and clustered melanosomes [22]. When the size of melanosomes is investigated, the largest ones are found in African skin, followed in order by Indian, Mexican, Chinese and European [22, 23]; those melanosomes that are distributed individually are of larger size than the clustered melanosomes [22].

When light hits the skin, the long wave lengths of light are preferentially absorbed by the melanin of the melanophages which characteristically are present in the dermis in ashy dermatosis, Shorter wave lengths are scattered by the collagen bundles, similar to scatter in the sky by various molecules composing the air, and the outcome is a bluish lesion to the human eye.

When light hits the skin, the long wave lengths of light are preferentially absorbed by the melanin of the melanophages, which characteristically are present in the dermis in ashy dermatosis. Shorter wave lengths are scattered by the collagen bundles, similar to scatter in the sky by various molecules comprising the air, and the outcome is a bluish lesion to the human eye.

It may be that the ashy color is related more to dark skin than to any specific property of the disease [3]. Whether this relates to melanosome number, size, distribution, melanization, or a combination of these is currently unclear.

The tendency of ashy dermatosis to appear in a variety of racial and ethnic groups of people with dark skin favors the hypothesis that ashy dermatosis is a result of the Tyndall effect in certain types of skin (Fitzpatrick types IV or V).

References

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