Aseptic and alopecic nodules of scalp (AANS), also known as pseudocysts of scalp, are a rare and emerging entity in literature. It is a nonscarring inflammatory alopecia characterized by multiple skin-colored dome-shaped nodules without any microbial colonization. In this article, we describe the clinico-trichoscopic and histopathological features of two cases of AANS.
A 40-year-old male presented with multiple painless, pruritic, raised lesions on the scalp associated with hair loss for 2 months. There was no history of trauma, insect bite, or application of any topical medication and no past history of nodular acne or other inflammatory lesions in flexural areas. Cutaneous examination revealed multiple, nontender, firm, dome-shaped skin-colored nodules, sized 1.5 to 5 cm, involving vertex and occipital area of scalp [Figure 1a]. On applying pressure to a nodule, there was no discharge from other sites. The bacteriological and mycological staining and cultures were negative. Ultrasonography revealed hypoechoic areas without any areas of collection or abscess formation. Trichoscopy showed black dots, yellow dots, broken hairs, vellus hair, and “Eastern pancake sign” corresponding to dilated follicular openings, honeycomb pigment network, and a pinkish hue in the background [Figure 1b and c]. Histopathology showed perifollicular inflammation comprising of neutrophils, plasma cells, and lymphocytes with pseudocyst formation, abundant foreign-body–type giant cells without dermal fibrosis. It showed intact pilosebaceous units, with a total of 14 including 5 hair follicles in the telogen phase, without any evidence of scarring [Figure 1d].
A 25-year-old male presented with a single pruritic nodule on the scalp, associated with hair loss, for 3 months. Cutaneous examination revealed a single skin-colored dome-shaped, nontender, firm nodule varying from 1.5 to 3 cm in diameter, with few terminal hairs and creamy white exudate [Figure 2a]. The fungal and bacteriological cultures were negative. Ultrasonography showed well-defined subcutaneous hypoechoic nodules, without any areas of fluid collection/abscess formation. Trichoscopy showed few black dots, dilated follicular openings, and twisting of hair shafts resembling pili torti [Figure 2b and c]. Histopathology revealed stratified squamous epithelium with no evidence of cyst formation, presence of perifollicular inflammatory infiltrate, intact pilosebaceous units without any areas of fibrosis [Figure 2d].
On the basis of clinical and histopathological findings, diagnosis of AANS was made. Both the patients were prescribed doxycycline 100 mg twice daily for 3 months and showed resolution of alopecia and nodules [Figure 3a and c]. Trichoscopy showed circle hair, short vellus hair, and absence of dilated follicular openings indicating regrowth [Figure 3b and d].
AANS is a relatively rare and underdiagnosed inflammatory nonscarring alopecia. The term AANS was coined by Abdennader and Reygagne in 2009, predominantly affecting young males aged 20 to 30 years. It is characterized by presence of one or few alopecic dome-shaped nodules, mainly located on the vertex and upper occiput, surrounded by normal scalp. The nodules are asymptomatic, but there may be mild pain, itching, or discomfort. Etiology of the condition is unknown. It is hypothesized that follicular occlusion leads to the formation of nodule or pseudocyst and the presence of deep folliculitis could possibly cause nonscarring alopecia. Granulomatous reaction secondary to immune response caused by follicular alteration or a foreign body or some unknown factor has also been considered.
Trichoscopic features of AANS are black and yellow dots, fine vellus hair, and broken hair shafts. Recently two trichoscopic signs have been described by Bourezane and Bourezane: “Eastern pancake sign” resulting in dilated follicular orifices and “comedo-like structures” resembling comedones corresponding to yellow and black dots.
AANS should be differentiated from dissecting cellulitis of scalp, clinically by the absence of painful pustules, nodules, abscess, or sinus tracts and histologically by the absence of abscess formation, destruction of the pilo-sebaceous units, and fibrosis. Ultrasonography shows the presence of hypoechoic areas without any areas of fluid collections/abscesses connecting hypoechoic fistulous tracts reaching the hair bulb. Unlike folliculitis decalvans, AANS does not present with multiple pustules and tufted folliculitis. Ruptured pilar cysts often mimic AANS, however, they are characterized by presence of multiple layers of keratinocytes without granular cell layer on histopathology.
Treatment modalities include a 3-month course of doxycycline (100-200 mg/day), intralesional corticosteroids, and aspiration or drainage of the nodule. Cases of spontaneous regression have been described, and in general, surgical excision is not necessary. It responds well to treatment and has a good prognosis. Hence, clinicians should be aware of this rare, probably unrecognized entity to avoid aggressive medical and surgical interventions.
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1. Abdennader S, Vignon-Pennamen MD, Hatchuel J, Reygagne P Alopecic and aseptic nodules of the scalp (pseudocyst of the scalp): a prospective clinicopathological study of 15 cases. Dermatology 2011: 222; 31–35.
2. Lázaro-Simó AI, Sancho MI, Quintana-Codina M, Del Alcázar Viladomiu E, Millet PU, Redonnet MS Alopecic and aseptic nodules of the scalp with trichoscopic and ultrasonographic findings. Indian J Dermatol 2017: 62; 515–8.
3. Rodríguez-Lobato E, Morgado-Carrasco D, Giavedoni P, Ferrando J Alopecic and aseptic nodule of the scalp in a girl. Pediatr Dermatol 2017: 34; 697–700.
4. Bourezane Y, Bourezane H Two new trichoscopic signs in alopecic and aseptic nodules of the scalp: “Eastern pancake sign”and comedo-like structures. Ann Dermatol Venereol 2014: 141; 750–5 [in French].
5. Brănişteanu DE, Molodoi A, Ciobanu D, Bădescu A, Stoica LE, Brănişteanu D, et al. The importance of histopathologic aspects in the diagnosis of dissecting cellulitis of the scalp. Rom J Morphol Embryol 2009: 50; 719–724.
6. Bellinato F, Maurelli M, Colato C, Gisondi P, Girolomoni G Alopecic and aseptic nodules of the scalp: A new case with a systematic review of the literature. Clin Case Rep 2021: 9; e04153.