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.
Leukonychia totalis. This is a rare nail disorder that is inherited in autosomal dominant fashion. The color of normal nail plates beyond the lunulae is largely pink from the blood in the blood vessels of the nail bed. The whiteness shown here is due to an abnormality in the nail plate. The nails may also be brittle.
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.
Klippel-Trénaunay-Weber syndrome. This is a condition in which vascular malformations, varicosities, and phlebectasia cover an entire limb or other body area. There may be associated skeletal abnormalities including macrodactyly and syndactyly. A combination of port-wine stain and vascular malformations may be present from birth. The osteohypertrophy develops during the first several years of life.