Solitary mastocytoma arising at a hepatitis B vaccination site

On the first day of life, a healthy infant was given a recombinant hepatiti s B vaccine. Over the following year, a 3 by 4.5 cm, well-defined, erythema tous patch with an overlying white, reticulated, smaller plaque gradually a ppeared on her thigh at the vaccination site. Darier's sign was elicited at the site. Examination of a biopsy specimen showed an upper dermal mast cel l infiltrate, This is the first reported case of a solitary mastocytoma app earing in a vaccination site.