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Acquired symmetrical dermal melanocytosis (naevus of Hori) developing after aggravated atopic dermatitis.

Murakami F, Soma Y, Mizoguchi M

Dermatology Division, Yokohama City Seibu Hospital, St Marianna University School of Medicine, Yokohama, Japan.

BACKGROUND: Acquired symmetrical dermal melanocytosis (ASDM) is a pigmentary disorder characterized by blue-brown macules most frequently seen on the face of young and middle-aged Asian women. ASDM developing after other skin diseases has not been previously reported. OBJECTIVES: To characterize the clinical and histopathological features of ASDM associated with atopic dermatitis (AD) and to elucidate the differences between AD-associated ASDM and idiopathic ASDM. METHODS: Sixteen patients with ASDM associated with AD were examined clinically and histopathologically and were compared with 69 patients with idiopathic ASDM. RESULTS: The AD patients associated with ASDM consisted of four men and 12 women with a mean age of 32.8 +/- 13.1 years. Most patients remembered that the pigmented macules appeared in places where refractory eczema had existed for a long time. The marked preponderance in females and the appearance in the early reproductive period were common features of AD-associated ASDM and idiopathic ASDM. AD-associated ASDM was most commonly observed on the forehead (68.8%) and on the backs of the hands (50.0%), whereas 89.9% of idiopathic ASDM was seen on the cheeks. There was no significant difference in the number of dermal melanocytes between AD-associated ASDM and idiopathic ASDM. Electron microscopic studies demonstrated many mature melanocytes and smaller numbers of immature melanocytes in the dermis. Some melanocytes were seen adjacent to mast cells. CONCLUSIONS: AD-associated ASDM does not appear to be rare in Japan. ASDM may be triggered in AD patients by sunlight exposure, some alterations in sex hormones and/or persistent cutaneous inflammation. Histamine and stem cell factor produced by mast cells may play crucial roles in the pathogenesis of AD-associated ASDM.

Published 12 May 2005 in Br J Dermatol, 152(5): 903-8.
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