Unusual inflammatory and hyperkeratotic halo naevus in children.

Although the classic halo naevus (HN) is a melanocytic naevus with a surrounding rim of depigmentation, these naevi can present unusual features. We describe an unusual and previously unreported variety of HN in children. Between March 1999 and September 2002, 14 children (11 boys and three girls, age range 6-14 years) were referred to us for evaluation of one or more 'inflamed' naevi. All the affected naevi showed the same clinical development: (i) after an initial inflammatory stage their surfaces gradually became thickened and rough, then (ii) verrucous and raised, and finally (iii) scaly crusted. A marked halo of depigmentation subsequently developed in all lesions, with simultaneous disappearance of the hyperkeratotic surface appearance. Lesions were multiple in five cases and single in nine, and were mainly located on the back (nine cases). Excisional biopsy was performed in eight cases. The biopsies were all taken in the 'prehalo phase'. In each case, histopathology revealed a compound melanocytic naevus, with additional features that varied depending on the clinical stage of the lesion. Immunohistochemical staining of the dense inflammatory infiltrate showed a predominance of CD3(+)/CD8(+) T lymphocytes, as usually occurs in HN. On the basis of these observations, we believe that the described naevi represent an unusual variety of HN in children. Knowledge of this possible clinical evolution of HN is important to avoid unnecessary surgical excision in these young patients.

Sensitization to thimerosal in atopic children.

Thimerosal is an organic mercurial compound widely used as a preservative in vaccines, eyedrops, and contact lens cleaning and storage solutions. 5 infants, 2 female and 3 male, ranging in age from 7 to 28 months and affected by atopic dermatitis (AD) diagnosed according to the Hanifin and Rajka criteria, experienced an exacerbation of their clinical condition 2-10 days after mandatory vaccinations with vaccines containing thimerosal. Cutaneous lesions of nummular eczema appeared on the trunk, limbs and face. All patients were patch tested with serial dilutions of thimerosal in petrolatum. A positive patch test reaction to thimerosal 0.1% pet. was observed in all 5 children. 3 of them also showed a positive reaction at 0.01% and 0.05% pet. Despite their thimerosal-hypersensitivity, all children completed the entire series of mandatory vaccinations, care being taken to use different needles for injection and aspiration of the vaccine. The 2-year follow-up did not reveal other episodes of exacerbation of the AD after vaccination. The present study confirms the high frequency of sensitization to thimerosal in atopic children and suggests that vaccination can cause clinical symptoms in sensitized children. Nevertheless, sensitization to thimerosal does not prevent children from continuing with mandatory vaccinations.