LPP is seen more commonly in women than men, and Caucasians are more often aff ected than African Americans. It presents with erythema, perifollicular scale, and scattered patches of scarring alopecia. Half of involved cases develop concomitant clinical features of lichen planus. When present, these characteristics may help distinguish it from FD and other scarring alopecias.6
The etiology of LPP is unknown, but is thought to be similar to the presumed cause of lichen planus: a T-cell?mediated autoimmune response that damages basal keratinocytes.5 Histologic findings include a band-like mononuclear cell infiltrate obscuring the interface between follicular epithelium and dermis at the superficial part of the follicle with occasional interfollicular epidermal changes consistent with lichen planus.
Inflammatory tinea capitis is a common dermatophyte infection of the scalp that aff ects children and adults alike. Typically, it is easily distinguished from FD. However, severe cases may result in a highly inflammatory pustular eruption with alopecia—with or without a kerion—which can make diff erentiation difficult.
In contrast to FD, the alopecia associated with tinea capitis is usually nonscarring, although this depends on the extent and depth of infection. Also, tinea capitis may present with either discrete patches or involve the entire scalp, whereas FD is usually localized to the vertex or occiput (as noted earlier). Correct diagnosis can be accomplished by means of light microscopy and fungal culture.
Secondary syphilis is usually a sexually transmitted disease, but it can also be acquired perinatally. It often presents with a “moth-eaten” alopecia and should be considered when examining patients with patchy alopecia such as that seen in FD. These lesions manifest 3 to 10 weeks after the onset of primary syphilis. Early in its course, the condition is reversible, but if it becomes chronic, the condition will cause a scarring alopecia.
The presence of other stigmata, including a generalized pruritic papulosquamous eruption with involvement of the palms and soles, mucosal lesions ranging from superficial ulcers to large gray plaques, and condylomata lata, should help to diff erentiate syphilis from FD.
Serologic tests such as rapid plasma reagin and venereal disease research laboratory assays are often preferred for routine screening. If the index of suspicion is high, confirmatory testing with direct antibody as-says such as a microhemagglutination assay or fluorescent treponemal antibody absorption test is indicated.