The diagnosis of scalp rosacea relies on the integration of clinical, trichoscopic, and histopathological findings, as previously outlined. A dermoscopy-guided biopsy is recommended in areas displaying follicles with peripilar scaling and dilated arborizing vessels. This approach is crucial for diagnostic accuracy, since chronic inflammation at the level of the follicular infundibulum and isthmus may induce papulopustular changes and peripilar scaling that closely resemble the features of folliculitis decalvans and lichen planopilaris [9, 10].

The classification of this condition within the rosacea spectrum is supported by the aforementioned findings together with its reported response to conventional rosacea therapies. Although scalp rosacea frequently occurs in association with facial disease, diagnosis should not be based solely on the presence of facial rosacea. Isolated scalp involvement has also been reported in the literature, indicating that facial rosacea is not a prerequisite for diagnosis.

The absence of validated diagnostic criteria highlights the need for further studies to better define this entity and distinguish it from other inflammatory scalp disorders.

Differential diagnosis of scalp rosacea is broad and includes causes of scalp erythema such as psoriasis, seborrheic dermatitis, contact dermatitis, lichen planopilaris, folliculitis decalvans, dermatomyositis, and discoid lupus erythematosus [1, 15]. All of these conditions may present with pruritus or a burning sensation in varying degrees. Frequently, discerning between scalp rosacea and these entities relies on the combination of clinical and trichoscopic findings. In some cases, a scalp biopsy may be required to confirm the diagnostic suspicion [15].

The main trichoscopic findings of the most relevant differential diagnoses of scalp rosacea are summarized below.

In psoriasis, characteristic trichoscopic features include diffuse silver-white scaling and perifollicular scaling, together with regularly distributed twisted red loops, dotted (glomerular) vessels, and punctate hemorrhages (hemorrhagic dots) [16, 17].

The main trichoscopic feature of seborrheic dermatitis is diffuse yellowish scaling. Thin, irregularly arranged arborizing and linear vessels, as well as red structureless areas, may also be observed [18].

In contact dermatitis, trichoscopy usually reveals diffuse white-yellowish scaling and yellow exudate, occasionally accompanied by perifollicular tubular scaling. The most common vascular patterns include dotted vessels, comma vessels, and single loops, frequently involving the hairline, retroauricular region, or neck [19, 20]. In this setting, a detailed history of recent scalp exposure to new products is essential for diagnosis.

Lichen planopilaris in diffuse pattern is characterized by perifollicular hyperkeratosis and hair casts, erythema, and white scarring patches with loss of follicular openings, findings not observed in scalp rosacea. Folliculitis decalvans may share some of these features; however, it more commonly presents with perifollicular pustules, yellowish crusts, and prominent tufted hairs [15, 20].

Among connective tissue diseases with scalp involvement, diffuse erythema represents the classical trichoscopic finding. Dermatomyositis shows prominent vascular alterations, particularly fine linear telangiectasias [21,22,23,24]. Peripilar casts and interfollicular scaling may also be present; however, follicular pustules are absent in contrast to scalp rosacea [12].

In discoid lupus erythematosus, trichoscopic features vary according to disease activity. Active lesions commonly exhibit red dots, blue-gray dots, and adherent scaling, whereas inactive/chronic disease more often shows structureless white areas with reduced follicular openings, exaggerated honeycomb pigmentation, and arborizing vessels. Follicular keratotic plugs and telangiectasia may be found in both stages with variable frequency [21].

In patients with systemic lupus erythematosus, trichoscopy most commonly reveals black dots, scattered brown pigmentation, a speckled blue-gray pattern, and prominent thick arborizing vessels [22, 23].

Acneiform eruptions of the scalp may also mimic scalp rosacea, particularly in patients with follicular papules or pustules on erythematous skin. Trichoscopy reveals central follicular pustules, yellow-brown crusts, and a lattice-like pattern of dilated vessels, often with perifollicular erythema and reactive scaling.

Unlike scalp rosacea, vascular changes are less uniform, and findings tend to reflect suppurative folliculitis, favoring an acneiform process when predominant [24].

Other differential considerations may include infectious processes—such as dermatophyte infections, Candida, Malassezia-associated dermatitis, or bacterial infestations—as well as non-infectious entities such as Ofuji syndrome and early-stage folliculitis decalvans, which may partially overlap in clinical or trichoscopic appearance [1, 15, 24].

To support diagnostic accuracy, Table 1 summarizes the clinical, trichoscopic, and histopathological features that differentiate scalp rosacea from other conditions that may present with scalp erythema.