Localized scleroderma (morphea) is a relatively benign skin condition, characterized by well-defined, round, irregular or linear sclerotic plaques. The disease affects all age groups, although the peak incidence is observed between 20-40 years of age. The etiology of morphea has not been yet fully understood, but there is evidence pointing towards autoimmune, hereditary, chemical and traumatic factors acting as causative agents. There is no standard treatment scheme in morphea and in less severe cases local therapy alone may be sufficient. Systemic therapy includes, among different measures repeated courses of intramuscularly (i.m.) administered procaine penicillin, which in many patients results in softening of affected skin.

We describe a case of a 40-year old patient with localized scleroderma, whose first course of i.m. treatment with a single dose (2 400 000 i.u.) of procaine penicillin was disturbed after 11 hours by the appearance of maculopapular exanthem, localized on the trunk and extremities, with coexistance of pruritus and oedema. Intradermal tests with penicilloylpolylysine (PPL) and 2% procaine performed before penicillin administration were negative after 15, 30 and 60 minutes and within 24 hours of observation.

3 months after the remission of skin lesions diagnostic procedures were performed including skin prick tests (negative with 2% procaine, PPL, benzylpenicillin (BP) and amoxicillin), intradermal tests (negative with 2% procaine, PPL, amoxicillin and positive after 3 hours with BP) and patch tests (negative with amoxicillin and ampicillin and positive after 48 hours with BP). Skin biopsy was obtained from the area of positive intradermal test result, showing mixed dermal inflammatory infiltrate with the majority of eosinophils.

Penicillins may be responsible for various types of allergic reactions, classified as immediate and nonimmediate, based on the time interval between drug administration and their onset. Both patch and intradermal tests are regarded by several authors as useful in evaluating delayed type hypersensitivity to penicillins, particularly maculopapular exanthems. In the case of our patient, maculopapular rash could be caused by minor penicillin determinant mixture (PPL - negative, BP - positive). Delayed hypersensitivity to beta-lactams is a long-lasting condition, therefore further observation of the described patient is planned in order to evaluate the duration of skin tests positivity.

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