Pediatric emergency medicine trisk 1812 1812

FIGURE 88.7 Spitz nevus.

Yellow, Tan, or Brown Papules
Many papules are yellow, tan, or brown. These include the lesions seen in
urticaria pigmentosa (see Chapter 69 Rash: Neonatal ), flat warts, xanthomas,
insect bites, juvenile xanthogranulomas (JXGs) as well as melanocytic nevi.
One way to differentiate the various papules from one another is to scratch
them. If hiving of a scratched lesion (Darier sign) occurs within a short period of
time (3 to 5 minutes), the lesion likely contains mast cells (i.e., a mastocytoma or
urticaria pigmentosa) ( Fig. 88.9 ). Make sure to scratch normal skin to rule out
the presence of dermatographism. The latter condition will produce a falsepositive Darier sign. When no urtication occurs, a biopsy may be helpful. Flat
warts tend to be grouped, are flat topped, and can be autoinoculated in scratch
lines (pseudo-Koebner phenomenon). Lesions characteristic for JXGs are not flat
topped, tend to be singular in number (or when multiple are scattered about), and
do not demonstrate the Koebner phenomenon (recapitulation of the eruption in