Humbled again: Alopecic and aseptic nodules of the scalp

By Warren R. Heymann, MD, FAAD
November 3, 2021
Vol. 3, No. 44

I confess. I had never heard of alopecic and aseptic nodules of the scalp (AANS) and have probably beaten around the bush with alternative (incorrect) diagnoses when confronted with probable cases.

In 1992, Iwata et al reported 19 Japanese patients, each with a solitary painful subcutaneous tumor with alopecia on the scalp and a histologically ill-defined cyst wall. They coined the lesion "pseudocyst of the scalp," and subsequent cases were reported in the Japanese literature. (1) The term AANS was coined by Abdennader and Reygagne in 2009 because in their retrospective review of 18 cases, pseudocysts were not always present. (2) A subsequent prospective study of 15 cases of AANS demonstrated that the disorder affected predominantly young (mean age 29.7 years), Caucasian (11/15), male (14/15) patients. The main location of the nodules was the occiput. The associated alopecia was nonscarring. Material from the puncture was aseptic. The histopathology showed a deep granuloma in 7 of 14 patients and a nonspecific inflammation in 7 patients. Of patients treated with doxycycline for 3 months, 8 patients were cured, and 3 others had a good response. (3)

Although usually observed in younger people, AANS may affect all age groups, being reported in children as young as 7-years-old to age 72 years. (4) Clinically, AANS presents as one or few, dome-shaped, firm or fluctuant and usually asymptomatic nodules on the vertex or occipital area associated with non-scarring alopecia and surrounding normal scalp. Drainage of the nodules reveals serous, bloody, or purulent exudate. Cultures are routinely negative. (5) Histopathology demonstrates a chronic lymphoplasmacytic infiltrate accompanied by multinucleated foreign body giant cells. (6) Trichoscopy may demonstrate broken hair shafts, black dots, yellow dots, and fine vellus hairs. These trichoscopic features are similar to alopecia areata but have also been described in early stages of dissecting cellulitis of the scalp. Ultrasonography displays a well-defined hypoechoic subcutaneous nodule. (7) The differential diagnosis may vary with the stage of the lesions — early raised lesions need to be differentiated from ruptured pilar cysts, dissecting cellulitis, bacterial folliculitis, folliculitis decalvans, or cutaneous metastases. Later lesions may resemble alopecia areata. Although most cases resolve in several months, recurrent episodes may occur for years, even in the same area, with hair regrowth within the nodules. (5,8)

The prognosis of AANS is good, with lesions resolving spontaneously, or responding to doxycycline, intralesional steroids, or aspiration and drainage of the lesions. (5)

Rodríguez-Lobato et al state: “The etiology of AANS is unknown and it is likely that the condition is underdiagnosed. Some hypotheses refer to follicular occlusion as the cause of the nodule or pseudocyst formation1or to a particular form of deep folliculitis leading to a nonscarring type of alopecia. An immune response that induces a granulomatous inflammation targeted against the hair follicle has also been considered. This granulomatous reaction might be secondary to a follicular alteration, a foreign body, or an immunologic response triggered by an unknown factor.” (4) Alopecia is nonscarring presumably because the granulomatous infiltrate is located around the lower portion of the follicle, beneath the bulge. (9)

I’m virtually certain that I have seen such cases, which I clearly failed to diagnose correctly. Fortunately, most patients have probably done well, despite my ignorance. That should not happen again, for AANS at least. With every passing day I realize how much I do not know — dermatology is a humbling affair and can never truly be mastered.

Point to Remember: Think about alopecic and aseptic nodules in the scalp — especially in younger patients who present with nodular lesions that evolve to resemble alopecia areata. Making the right diagnosis will alleviate anxiety and most patients have a good prognosis with straightforward therapeutic maneuvers.

Our expert’s viewpoint

Sami Abdennader, MD
Consultant at the Sabouraud Center, Saint-Louis Hospital, Paris

Alopecic and aseptic nodules of the scalp (AANS) is a new clinical entity characterized by one or several nodules mainly located in the occiput. The alopecia on the surface of the nodules is nonscarring and the material obtained by puncture is sterile. The main differential diagnosis is dissecting cellulitis of the scalp (DCS). Other clinical differential diagnoses include inflamed trichilemmal cyst and metastatic nodule of the scalp. After biopsy, the histopathology shows granuloma in the deep dermis in half of the cases. In another half of the cases we found a nonspecific deep lymphohistiocytic infiltrate. We never found an image of pseudocyst as described in the Japanese cases, first reported by Iwata & al. in 1992. Racial factors with a different type of hair or less deep specimens for histological purpose in our cases might explain these findings.

The treatment with doxycycline 100mg/day for at least 3 months is efficient in the majority of patients. This treatment induces the resolution of the nodules and hair regrowth. Other therapeutical options include repetitive punctures and local injection of steroids.

The etiology of AANS is unknown. A follicular occlusion is possible as is the case in DCS. The typically granulomatous infiltrate might be induced by an immunological process as is the case in alopecia areata.

In conclusion, clinicians should be aware of this rare and probably unrecognized entity to avoid aggressive surgical procedure.

1. Tsuruta D, Hayashi A, Kobayashi H, Nakagawa K, Furukawa M, Ishii M. Pseudocyst of the scalp. Dermatology. 2005;210(4):333-5. doi: 10.1159/000084761. PMID: 15942223.

2. Abdennader S, Reygagne P. Alopecic and aseptic nodules of the scalp. Dermatology. 2009;218(1):86; author reply 87. doi: 10.1159/000165608. Epub 2008 Oct 22. PMID: 18946198.

3. 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 Feb;222(1):31-5. doi: 10.1159/000321475. Epub 2010 Nov 24. PMID: 21099195.

4. Rodríguez-Lobato E, Morgado-Carrasco D, Giavedoni P, Ferrando J. Alopecic and aseptic nodule of the scalp in a girl. Pediatr Dermatol. 2017 Nov;34(6):697-700. doi: 10.1111/pde.13293. Epub 2017 Oct 16. PMID: 29044722.

5. Puerta-Peña M, Rodríguez-Peralto JL, Ortiz-Romero PL, Velasco-Tamariz V. Rapidly-developing alopecic nodules in a young man. Int J Dermatol. 2020; 59: 1219-1221. doi: 10.1111/ijd.14847. Epub ahead of print. PMID: 32181494.

6. Gupta I, Dayal S, Kataria SP. Aseptic and Alopecic Nodules of Scalp: A Rare and Underdiagnosed Entity. Int J Trichology. 2018 Sep-Oct;10(5):231-233. doi: 10.4103/ijt.ijt_30_18. PMID: 30607043; PMCID: PMC6290287.

7. Garrido-Colmenero C, Arias-Santiago S, Aneiros Fernández J, García-Lora E. Trichoscopy and ultrasonography features of aseptic and alopecic nodules of the scalp. J Eur Acad Dermatol Venereol. 2016 Mar;30(3):507-9. doi: 10.1111/jdv.12903. Epub 2014 Dec 10. PMID: 25492415.

8. Al-Hamdi KI, Saadoon AQ. Alopecic and Aseptic Nodules of the Scalp with a Chronic Relapsing Course. Int J Trichology. 2019 Nov-Dec;11(6):244-246. doi: 10.4103/ijt.ijt_106_19. PMID: 32030060; PMCID: PMC6984049.

9. Abdennader S, Reygagne P. Alopecic and aseptic nodules of the scalp. Dermatology. 2009;218(1):86; author reply 87. doi: 10.1159/000165608. Epub 2008 Oct 22. PMID: 18946198.