JAMES M.GRICHNIKMD, PhD
Dermatology has an illustrious history of formulating visual clues to facilitate diagnosis of oft-confused conditions. From the opulent (“crown-of-jewels”) to the mundane (“apple jelly”), dermatologists have consistently drawn inspiration from the physical world when classifying disease. We intend to add to this literature by submitting a novel visual clue to aid in the diagnosis of hypertrophic lichen planus.
Given a causal linkage with the hepatitis C virus and recent case reports of malignant transformation, hypertrophic lichen planus requires astute and careful consideration.1,2 The condition is marked by firm, elevated, hyperkeratotic, red-brown to purple-gray plaques with chalky-white scale and follicular accentuation that imparts a geologic appearance to affected skin (Figure 1). Lesions thus bear a striking resemblance to the extrusive (or rapidly cooled) variants of igneous rock (Figure 2), characterized by a fine-grained (or aphanitic) texture with the occasional vesicular (pocked) surface and variable colors from dark pink to gray-black.3,4 The igneous rock sign has been a useful adjunct in several cases (Figure 3) to help differentiate hypertrophic lichen planus from other members of the papulosquamous differential, and we hope that it becomes a valued visual clue in the armamentarium against dermatologic disease.
Welsh JP, Skvarka CB, Allen HB. A Novel Visual Clue for the Diagnosis of Hypertrophic Lichen Planus. Arch Dermatol. 2006;142(7):954. doi:10.1001/archderm.142.7.954