Gingival hyperplasia from phenytoin. The mechanisms of adverse reactions to drugs vary. Some, like the urticarial or eczematous, are clearly based on an allergic or immunologic mechanism; others are utterly obscure in mechanism. Such is the gingival hyperplasia caused by phenytoin. Since it occurs in almost all patients receiving the drug, all one can say is that the effect probably is within the normal pharmacologic action of the drug.
Urticaria, also known as hives, is an outbreak of swollen, pale red bumps or plaques (wheals) on the skin that appear suddenly -- either as a result of the body's adverse reaction to certain allergens, or for unknown reasons.
Lichen striatus. This is a common and benign self-limited childhood dermatosis that is easily diagnosed from its classic appearance. Onset is usually between the ages of 3 and 10 years, and it is rare in young infants, adolescents, and adults. The lesions consist of pink, flesh-colored, or slightly hypopigmented flat-topped papules that evolve in a linear array following lines of Blaschko. The linear course of the papules may eventually traverse the major part of an extremity. The area of involvement is often noted to become wider as it advances and may even include the nails.
Lyme disease is a bacterial infection transmitted by a tick Lyme disease was first recognized in 1975 after researchers investigated why unusually large numbers of children were being diagnosed with juvenile rheumatoid arthritis in Lyme, Connecticut and two neighboring towns.
The eruption shown was unusual in that it was so widespread and vesiculopustular. Occasionally, this unimportant eruption must be differentiated from more serious infectious processes, such as neonatal herpes simplex. Tzanck smear of a pustule of erythema toxicum neonatorum will reveal numerous eosinophils but no multinucleated giant cells or bacteria. Occasionally, peripheral eosinophilia is also present. The cause of this condition is not known, and it resolves spontaneously within 10 days. No treatment is required.