**9. Scarring alopecia**

**6. Horizontal sections**

16 Skin Biopsy - Diagnosis and Treatment

Horizontal sections are becoming the method of choice as they offer the advantage of evalu‐ ating large numbers of follicles simultaneously, determining hair density, location of inflam‐ matory infiltrate and anagen to telogen ratio [5]. A transversely sectioned specimen will include all the hair follicles present in the biopsy, and in the same section. Although the clinical impression is very important in diagnosing alopecia, transversely sectioned biopsy specimens

can greatly aid the diagnosis and management of patients with alopecia [6].

**Figure 3.** Transverse section from a scalp biopsy from a patient with DLE.

**7. Hematoxylin and eosin staining of scalp biopsy**

The histological findings in many forms of hair loss may be similar, and an accurate diagnosis of hair loss depends on distinguishing abnormal from normal follicular architecture. It is important to identify the normal hair follicle structure, the number, size and distribution of hair follicles within a biopsy specimen. Hematoxylin and eosin staining of the scalp biopsies is the usual satin in most of the cases of hair loss, but in some of the alopecias (such as DLE), immunofluorescence staining may be needed to add in diagnosis. In addition, the pathologist may use additional special stains to narrow a differential diagnosis or confirm an initial impression and one of these is immunohistochemistry which is dependent on the localization

Histologically, cicatricial alopecia is characterized by dermal scarring, along with absent or reduced hair follicles and reduced number of erector pili muscles. But taking skin biopsy from the active area will be more informative about the diagnosis.

This scarring alopecia may be secondary, and due to numerous etiologies (such as due to infectious causes (Fig 4), or primary, where the cause and pathogenesis are largely unknown, but the target is the hair follicle itself (such as DLE and LPP).

The discussion in following sections is about the primary type as the skin biopsy is more informative about the diagnosis.

**Figure 4.** Scarring alopecia in a child secondary to tinea capitis.
