Diagnostic value of histopathologic examination in alopecias

Abstract

Alopecias are evaluated in two groups, namely noncicatricial type and cicatricial type. Cicatricial alopecias are generally irreversible due to the permenant damage to the hair follicles and as follicular epithelium is replaced by connective tissue in the late stages. In noncicatricial alopecia, the follicular epithelia is intact and hair regrowth is likely. The accurate diagnosis of alopecia subtypes which have different etiologies and occasionally result in permanent hair loss is of paramount importance to initiate the appropriate treatment in the early stages. Most of the subtypes of alopecia can be diagnosed with a detailed history and clinical evaluation. However, most of the disorders leading to alopecia present with nonspecific and overlapping clinical findings which alter over the course of the disease. In those instances, scalp biopsy and histopathologic evaluation is necessary to make or confirm the diagnosis. Transverse and vertical sections used for the interpretation of scalp biopsy specimens offer different advantages. Therefore, idealy, obtaining two 4 mm punch biopsy samples and combining both methods is suggested to enhance the diagnostic yield in patients with alopecia. In this review, the value of scalp biopsy in the diagnosis of subtypes of alopecia, the significance of evaluation of transverse and vertical sections in the histopathologic examination and the major histopathologic findings of the disorders involved in the etiology are described.