Erosive Pustular Dermatosis of the Scalp: A Clinicopathologic Study of Fifty Cases

Abstract

Erosive pustular dermatosis of the scalp (EPDS) is an uncommon, pustular, idiopathic disorder typically occurring on the scalp of the elderly, whose diagnosis requires close clinicopathologic correlations. Recently, the primary histopathologic characteristic of EPDS has been identified in some biopsies from hair-bearing scalp lesions as a sterile, vesiculo-pustule involving the infundibulum of hair follicles. To further delineate the clinicopathologic spectrum of the disease, we led a retrospective study of 50 patients (36 males and 14 females) with a diagnosis of EPDS between 2011 and 2021, reviewing clinical and histopathological data. Androgenetic alopecia was present in 32 patients. Triggering factors were present in 21 patients. The vertex was the most common location; one patient also had leg involvement. Two cases were familial. Disease presentation varied markedly from tiny, erosive, scaly lesions to crusted and hemorrhagic plaques, mimicking pustular pyoderma gangrenosum (PPG). Biopsies of patients with severe androgenetic or total baldness produced specimens showing nonspecific pathologic changes (39/50), while in 11 patients with a hair-bearing scalp histopathologic examination, changes were specific. The clinicopathologic similarities between EPDS and PPG suggest that EPDS should be included in the spectrum of autoinflammatory dermatoses. Clinicians could consider the possibility of associated disorders rather than managing EPDS as a sui generis skin disorder.

Keywords: erosive pustular dermatosis; histology; neutrophilic dermatoses; pathergy; pustular spongiotic infundibular folliculitis; pyoderma gangrenosum; scalp.

Figure 1

Erosive pustular dermatosis of the scalp; (A) solitary eroded and crusting lesions localized on the vertex. Diagnostic consideration was squamous cell carcinoma; (B) diffuse scalp involvement of tiny, erythematous, slightly erosive and keratotic papules simulating actinic keratoses.

Figure 2

Erosive pustular dermatosis of the scalp; (A) thickened keratotic plaques on atrophic skin on the vertex; (B) severe clinical presentation with diffuse, thickened, dried yellow crusts, with a greenish or blackish hue resembling pustular pyoderma gangrenosum.

Figure 3

Erosive pustular dermatosis of the scalp; (A) erosions and crusts with a few follicular pustules; (B) partly eroded skin with underlying superficial folliculitis. A subepidermal clefting is evident (arrow); (C) perifollicular and interfollicular fibrosis; (D) total destruction of the upper portion of a follicular infundibulum by suppuration with retained hair shaft.

Figure 4

Erosive pustular dermatosis of the scalp; (A) follicle-based vesiculo-pustules and erosions; (B,C) vesiculo-pustules at top of follicular orifices, with sparing of interfollicular epidermis; (D) the vesicle contains numerous polymorphonuclear cells.

Figure 5

Erosive pustular dermatosis of the scalp; (A) scarring alopecia and erosions with presence of follicular pustules, lakes of pus and tufted hairs at the expanding margins (arrow); (B) multiple adjacent infundibula showing intrafollicular and perifollicular suppuration; (C) perivascular infiltrate of neutrophils with hints of vasculitis. The confluence of multiple vesiculo-pustules at intraepidermal level results into an intraepidermal blister; (D) two follicles converge toward a common opening above the entrance of the sebaceous duct.

Figure 6

Erosive pustular dermatosis of the scalp; (A) tiny erosions, scale crusts and scarring. Pustules are barely detectable; (B) diffuse dermal fibrosis. A miniaturized hair follicle at the right lateral margin is seen (arrow); (C) dermal inflammatory infiltrate of lymphocytes and neutrophils; (D) intraepidermal spongiform pustule (arrow).

Figure 7

Erosive pustular dermatosis of the scalp; (A) chronic, long-standing EPDS with diffuse scarring alopecia. A solitary, erythematous, eroded and crusted plaque was biopsied in the suspicion of squamous cell carcinoma (arrow); (B) hemorrhagic blistering in the dermal–epidermal junction, subepidermal clefting and diffuse dermal fibrosis. Note elastotic material pushed down into the deep reticular dermis (arrow); (C) focal aggregates of macrophages and foreign-body giant cells containing small hair fragments within deep reticular dermis; (D) particular of C.

Figure 8

Erosive pustular dermatosis of the scalp; (A) black-greenish crusted plaque on the vertex; (B) removal of the crust evidences a reddish, raised, undermined border with a purulent granulation base, resembling pyoderma gangrenosum. The lesion was completely excised (C) specimen from the margin shows intrafollicular spongiform pustules (arrow); (D) specimen from the center evidences erosion with granulation tissue and neutrophilic micro-abscesses within the epithelium of regenerating hair follicles (arrows). The continuing activity of the disease may be inferred by the spongiform pustulation observed in the newly forming hair follicles at the top of the early granulation tissue.