An 8-year-old Hispanic boy presents for evaluation of mildly itchy, pinpoint bumps that have been present for 2 to 3 months. The “rash” is primarily involving the patient’s trunk. Patient is otherwise healthy, and no one else at home has a similar eruption. The mother of the patient has tried some over-the-counter hydrocortisone, which has helped some with the mild itching, but the lesions persist. The pediatrician noted the linear pattern of the pinpoint papules and made the clinical diagnosis of lichen nitidus (Figure 139-1). These lines represent the Koebner phenomenon caused by scratching done by the child in areas that are reachable.
Lichen nitidus with several linearly arranged groups of tiny, skin-colored papules amidst a background of scattered pinpoint papules on the trunk of a child. The linearly arranged groups of papules are secondary to scratching (Koebner phenomenon). (Used with permission from John Browning, MD.)
Lichen nitidus and lichen striatus are two distinct entities under the umbrella of lichenoid dermatoses, a grouping that is based on clinical findings resembling lichen planus, the prototypical lichenoid dermatosis, and the characteristic histologic findings of a band-like inflammatory infiltrate with or without vacuolar alteration of the dermoepidermal junction. Both conditions can present in a linear array; lichen nitidus because it exhibits the Koebner phenomenon (Figure 139-1) and lichen striatus (Figure 139-2) because it follows the lines of Blaschko. We will further discuss some of the similarities and distinguishing features of these two entities.
Lichen striatus with a curvilinear configuration of pink, slightly scaly, flat-topped papules on the upper extremity of a young girl. (Used with permission from Richard P. Usatine, MD.)
Lichen striatus—Linear lichenoid dermatosis, Blaschko linear acquired inflammatory skin eruption (BLAISE).
Lichen nitidus is a relatively rare disorder, more common in children and young adults.
Lichen nitidus often presents in preschool and school-aged children.
There does not seem to be a race or sex predilection.
Lichen striatus is seen primarily in children 5 to 15 years of age.1
Females are more often affected than males, with some reports of a female to male ratio as great as 2-3:1 (Figure 139-3).
Lichen striatus with a Blaschkoid distribution of pink, slightly scaly papules on the leg of an 11-year-old girl. (Used with permission from Richard P. Usatine, MD.)
Etiology and Pathophysiology