General Pediatrics Case
A 14-year-old boy is seen in the pediatric office with a 14-day history of rash.
He reports that the first lesion (Photograph A) began on his lower back and then additional lesions developed a few days later (Photograph B). He reports the rash is slightly pruritic, but denies fever, nausea, vomiting, headache, or musculoskeletal symptoms. His past history is positive only for mild seasonal allergic rhinitis for which he occasionally takes over-the-counter antihistamines. His vaccines are current. He is doing well in school, plays football, and denies sex, alcohol, and drug use. On physical examination he has a temperature of 37°C (98.5°F), a heart rate of 92 beats per minute, a respiratory rate of 16 breaths per minute, and a blood pressure of 110/69 mm Hg. The mucous membranes are moist and without lesions. The chest is clear. Heart has a normal S1 and S2 without murmur. The genitourinary examination is normal Tanner 4. The rash on the abdomen and back are slightly raised at the edges with a somewhat scaly appearance in the center.
Which of the following is the most likely diagnosis?
A. Contact dermatitis
B. Pityriasis rosea
C. Seborrheic dermatitis
D. Lichen planus
The correct answer is B.
Pityriasis rosea is a benign condition that usually presents with a herald patch, a single round or oval lesion appearing anywhere on the body. Usually about 5 to 10 days after the appearance of the herald patch, a more diffuse rash involving the upper extremities and trunk appears. These lesions are oval or round, slightly raised, and pink to brown in color. The lesion is covered in a fine scale with some central clearing possible. The rash can appear in a Christmas tree pattern on the back, identified by the aligning of the long axis of the lesions with the cutaneous cleavage lines. The rash lasts 2-12 weeks and can be pruritic. This rash is commonly mistaken for tinea corporis, and the consideration of secondary syphilis is important. Treatment is usually unnecessary but can consist of topical emollients and oral antihistamines, as needed. More uncommonly, topical steroids can be helpful if the itching is severe.
Lichen planus is rare in children. It is intensely pruritic, and additional lesions can be induced with scratching. The lesion is commonly found on the flexor surfaces of the wrists, forearms, inner thighs, and occasionally on the oral mucosa.
Seborrheic dermatitis can begin anytime during life; it frequently presents as cradle cap in the newborn period. This rash is commonly greasy, scaly, and erythematous and, in smaller children, involves the face, neck, axilla, and diaper area. In older children, the rash can be localized to the scalp and intertriginous areas. Pruritus can be marked.
Contact dermatitis is characterized by redness, weeping, and oozing of the affected skin. The pattern of distribution can be helpful in identification of the offending agent. The rash can be pruritic; removal of the causative agent and use of topical emollients or steroids is curative.
Psoriasis consists of red papules that coalesce to form plaques with sharp edges. A thick, silvery scale develops on the surface and leaves a drop of blood upon its removal (Auspitz sign). Additional lesions develop on scratching older lesions. Commonly affected sites include scalp, knees, elbows, umbilicus, and genitalia.
(Hay et al, p 397. Kliegman et al, p 2262. McMillan et al, pp 839-840. Rudolph et al, p 1262.)