Examination of the scalp, hair, nail, mucous membranes, and lymph nodes can provide additional diagnostic clues for any given eruption. Furthermore, the scalp, hair, nails, and mucous membranes may be the sole site of disease involvement. A former resident of mine, now a respected colleague, coined the mnemonic “GIFTs” for this diagnostic box of the wheel of diagnosis, where GIFT stands for “gleaning information from the” scalp, hair, nails, and mucous membranes, as well as from examining the lymph nodes. Examining these areas can be like gifts to the diagnostician, in that they may be replete with diagnostic information. Each of these anatomic sites and structures will be considered in turn in this chapter.
Some dermatoses characteristically involve the scalp and may cause alopecia. Diagnostic clues can be found in the expression of the disease itself. Examples here include papulosquamous presentations, such as the perifollicular scale and erythema of lichen planopilaris, or dermal reaction pattern presentations, such as the brownish or sometimes reddish plaques of scalp sarcoidosis.
Additionally, scalp disease may lead to scarring or nonscarring alopecia, and each disease state has a characteristic outcome, such as the scarring alopecia that accompanies discoid lupus erythematosus (DLE) or the nonscarring alopecia that may eventuate in tinea capitis. Some dermatoses can cause nonscarring loss early in the disease course, and ultimately scarring alopecia if the disease is severe or untreated, such as in kerion. Of note, the distinction between scarring and nonscarring alopecia is not always easy to discern. When examining the scalp, look for preservation of hair follicle openings at regular intervals in the affected area and compare this to a nonaffected area. In the earliest forms of scarring alopecia, there may be “follicular dropout”—an interruption to the regularity of follicles and the presence of small, scarred areas where no follicles can be seen. A dermatoscope can assist greatly in this determination.
Follicular dropout is an early sign of scarring alopecia. This sign may be difficult to discern. A dermatoscope can help.
Table 13.1 provides a differential diagnosis of scalp dermatoses by reaction pattern. Each reaction pattern is further subdivided according to whether scarring or nonscarring alopecia is characteristically present. The scalp dermatosis itself or the accompanying alopecia may be the primary presenting manifestation of scalp disease, or both may be equally prominent. In some cases, as in folliculitis, or the presence of small benign neoplasms, no alopecia is seen. This third category is also outlined in Table 13.1.
TABLE 13.1.Differential Diagnosis of Scalp Dermatoses and Their Typical Patterns of Alopecia ||Download (.pdf) TABLE 13.1. Differential Diagnosis of Scalp Dermatoses and Their Typical Patterns of Alopecia
|DISEASE ||NONSCARRING ALOPECIA ||SCARRING ALOPECIA ||NO ALOPECIA |
|✓ || || |
Early or mild