A Pruritic, Polygonal, Papular, Rash on a 10-year-old Boy

March 11, 2016

The eruption has become widespread over a 2-week period. Use your memory of dermatology basics to help make the diagnosis.

The Tale of a Male with a Pruritic, Polygonal, Papular, Planar Rash

The afternoon's first case in the acute care clinic promised to be "real challenge" to your dermatology skills.

A 10-year-old boy with past history of nummular eczema presents with 2-week history of rash that progressed from erythematous planar papules to larger polygonal, violaceous plaques that were purple and pruritic.

Mother denies any oral medications, history of contact exposures. Immunizations are up-to-date, medical history is “normal.”

Purple, polygonal papules and plaques.

Close-up of purple, polygonal papules and plaques.

Pruritic purple, polygonal, planar papules and plaques.

Papules, plaques are also seen on the penis.

Oral cavity showing a white, lacey pattern on the buccal mucosa.

Differential diagnosis for pruritic, purple popular rash: Guttate psoriasis, lichen planus, lichen nitidus, pityriasis rosea, tinea corporis, plaque psoriasis, lichen simplex chronicus.

Diagnosis: Lichen planus.

The 6 Ps of lichen planus: purple, polygonal, pruritic, planar, papules, plaques â sometimes including the penis.

Lichen planus: chronic inflammatory cell-mediated immune response of unknown origin. It may be found with other diseases of altered immunity.

Lichen planus overview: affects skin, oral and genital mucosa, scalp, nails. Acute onset; lesions covered by Wickham striae; scalp lesions can progress to scarring alopecia.

Lichen planus: clinical diagnosis; biopsy useful in atypical presentations; “saw-tooth” epidermal hyperplasia; hyperparakeratosks, T-cell infiltration at dermal-epidermal junction.

May cause lichen planus-like eruptions: arsenic, gold, PAS, isoniazid, quinidine, streptomycin, diabinase, phenothiazides, salts in color film.

Lichen planus: usually self-limited; typically resolves within 8-12 months. Treat mild cases with fluorinated topical steroids.

Lichen planus: seen infrquently in primary care practice; consult with dermatology is recommended.

It's after lunch in the acute care clinic and your nurse opens the afternoon by telling you that a difficult dermatology case awaits. You're no stranger to this kind of challenge and enter the exam room with great confidence.The patient: a 10-year-old boy with a history of numular eczema and a recent 2-week history of a widespread rash. Follow the case and its clues in the slides above. You may need to draw on your memory of medical school Derm 101 to generate your diagnosis.