DERMADIAGNOSIS

Lesions’ Pattern Helps Line Up Diagnosis

ix months ago, a 6-year-old records provided by his primary boy developed asymptom- care provider’s office. Satic lesions on his elbows, The lesions are particularly then his knees. They slowly spread numerous over the extensor sur- to other areas, including his fore- faces of the legs—especially the arms. One primary care provider knees—but are also seen on the diagnosed probable ; an- extensor forearms and elbows. other, molluscum. The prescribed The lesions are exquisitely -dis treatments—liquid nitrogen and crete, identical, tiny white pin- tretinoin, respectively—had no point , all with flat tops. effect. None are umbilicated. In several The boy’s mother became areas of the arms, linear collec- alarmed when the lesions started tions of lesions, some extending to form in long lines on his arms. as long as 6 cm, are noted. The At that point, she decided to bring rest of his exposed type V skin is him to for evalua- unremarkable. tion. Aside from his skin condi- The most likely diagnostic ex- tion, the child is healthy, accord- planation for these lesions is ing to both his mother and the a) b) Lichen nitidus Joe R. Monroe, c) Warts MPAS, PA, ­practices d) at Dawkins ­Dermatology Clinic in Oklahoma City. ANSWER He is also the The correct answer is lichen niti- founder of the dus (choice “b”), a harmless, self- Society of ­Dermatology limited condition of unknown ­Physician ­Assistants. origin. The lesions’ flat-topped

10 Clinician Reviews • FEBRUARY 2015 clinicianreviews.com (planar) surfaces and tendency best way to highlight it is with ent in this manner are , to form in linear configurations a short blast of liquid nitrogen. et atrophicus, along lines of trauma (so-called (Usually, though, the planar sur- and . ) are also faces of LN are sufficient to distin- features seen in lichen planus guish it from other conditions.) TREATMENT/PROGNOSIS (choice “d”) lesions; however, the In the United States, the term Our LN patient did not require latter are almost always pruritic Koebner phenomenon refers to any treatment, nor was any pos- and purple in color. Ironically, the the tendency for lesions to form sible. The condition is quite likely histologic pattern seen in both is along areas of trauma, usually in to clear on its own, leaving little if almost identical. a linear configuration. All four any evidence in its wake. An extremely common condi- items in our differential can pres- I often show affected patients tion, molluscum contagiosum ent in this way. However, the term and/or their parents pictures of (choice “a”) presents with mul- auto-inoculation might be more these types of conditions from our tiple tiny papules. But these are properly applied to conditions textbooks, for added reassurance. not planar, and most will have an such as warts and molluscum, And in this day and age, I direct umbilicated center. See the Dis- since the trauma has merely inoc- them to websites where they can cussion for ways to distinguish it ulated the organism into the skin. do more investigation on their from lichen nitidus. Inflammatory conditions such as own time. Flat warts (choice “c”), known LN and lichen planus are not truly The effective practice of- der as verruca plana, can strongly “spread” by the trauma. matology (and of all medicine, resemble lichen nitidus, but they Linearly configured lesions are for that matter) includes more are not as flat-topped and do not sufficiently unusual in dermatol- than merely making a correct di- appear white. They do Koebner- ogy to warrant their own differen- agnosis: I believe we’re obliged to ize, however, which occasionally tial. Among those that can pres- “sell” it as well. CR makes the distinction difficult.

DISCUSSION Follow us on Lichen nitidus (LN) is an unusual but benign condition primar- Facebook ily affecting children and young adults. Due to the contrast, the and Twitter! white planar papules are easier to see on darker skin. As is the case with many dermatologic di- Stay up-to-date on the latest health care agnoses, LN is easily identified if you’ve heard of it and therefore trends from Clinician Reviews! Find all of our know what to expect—but much more difficult if you haven’t. content in one spot, just for you. The latest LN’s unique manifestation dermatology cases, radiology reviews, and distinguishes it from other items in the differential. For example, ECG challenges are just a click away. molluscum and LN can easily be confused, especially since both Like us on Facebook at primarily affect children. But the facebook.com/ClinRev and pathognomic central umbilica- follow us on Twitter @ClinRev! tion of molluscum lesions is the key distinguishing feature; the

clinicianreviews.com FEBRUARY 2015 • Clinician Reviews 11