Skin Disorders Guide

Several of the nonvesicular viral exanthems including rubella and rubeola are characterized by the presence of red macules 1 to 2 cm in diameter. The occurrence of such lesions in the setting of characteristic clinical symptoms and signs allows for correct diagnosis. Roseola (exanthem subitum), recently found to be caused by human herpesvirus 6 is likewise associated with red macules shortly after a high fever has defervesced.Infection with parvovinls B 19 causes erythema infectiosum (fifth disease) in which bright red erythema of the cheeks (”slapped cheeks”) is later followed by a reticular erythema of the lateral arms. Red macules of the trunk and extremities are seen in about 10% of patients with infectious mononucleosis resulting from Epstein-Barr virus infection. Administration of antibiotics (especially ampicillin) to patients with “mono” increases the likelihood of developing an exanthem.

The lesions associated with all of these infections overlap in morphology with the vascular reactions described . They should probably be relisted there also.

The lesions of pityriasis rosea are occasionally devoid of visible scale. The possibility of pityriasis rosea should be considered in any patient who has 30 or more inflammatory papules located mainly on the trunk. A careful search usually reveals a few typical oval lesions, but if such are not present, secondary syphilis and pityriasis lichenoides should also be considered.

Pityriasis lichenoides is a rare disease in which patients develop crops of dome-shaped, red papules 2 to 6 mm in size. As the name implies, very fine scale may be present, but often no scale can be appreciated clinically. Ten to fifty individual papules may be present at anyone time. No oral lesions are present, and the extremities as well as the trunk are usually involved. The condition is chronic and lasts for months to years. In the acute type of pityriasis lichenoides (Mucha-Habermann disease) the papules may appear somewhat vesicular or even eroded, and some may heal with scarring.

A considerable proportion of the patients with secondary syphilis will have int1ammatory papules 2 to11 mm in diameter that are clinically devoid of scale. Such emptions can easily be mistaken for insect bites, pityriasis rosea, and pityriasis lichenoides. Patients with lesions such as these should be examined carefully for condylomata latamucous patches, hair loss, lymphadenopathy, and papular lesions of the palms and soles. A serologic test for syphilis should, of course, also be obtained.

Patients with Grover’s disease develop 30 or more small (2­ to 4-mm) red papules on the trunk, especially the back. Pruritus is usually significant. The histologic findings are diagnostic. The cause is unknown, but heat seems to be associated with the appearance of the lesions.

Children with scabies sometimes develop persistent red papules or nodules on the lower trunk and around the genitalia. These lesions do not clear with conventional therapy but do eventually undergo spontaneous resolution 6 months or so after the infestation is treated. This condition, known is nodular scabies, probably occurs as an immunologic reaction 10 mite proteins left at the site of the burrows.