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Underarm Eruption in a Teenaged Boy


Topical steroids and antifungals have not only failed to resolve the bilateral rash; the teen says they’ve made it worse. Your Dx?

[[{"type":"media","view_mode":"media_crop","fid":"51311","attributes":{"alt":"","class":"media-image media-image-right","id":"media_crop_6957107942425","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"6327","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"height: 279px; width: 370px; float: right;","title":"Figure 1. ","typeof":"foaf:Image"}}]]A healthy 16-year-old boy presented with a rash of several months’ duration that involved the bilateral axilla. The eruption appeared after he began participating in sports, at which time he started using over-the-counter antiperspirant/deodorant. When the eruption appeared he applied numerous topical medications including several topical steroid and antifungal creams without improvement. He felt these medications increased his discomfort. The patient’s personal and family histories were non-contributory.

Physical examination revealed light brown hyperkeratotic coalescing papules and plaques bilaterally in the axillae (Figure 1, above).

What is the best way to establish the diagnosis?

A. Fungal culture

B. KOH stain

C. Skin biopsy with H and E (correct answer)

D. Skin biopsy with PAS

E. Wood's lamp exam to check for fluorescence


The clinical differential diagnosis includes the following. What is your diagnosis?

A. Erythrasma

B. Pemphigus vegetans

C. Granular parakeratosis

D. Pytiriasis amiantacea (variant of psoriasis)

E. Darier’s disease

F. Hailey-Hailey disease

Please leave your answers below

Click here for answers and discussion.


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A hematoxylin and eosin (H&E) skin biopsy of the right axilla revealed marked hypergranulosis with prominent overlying compact parakeratosis (Figure 2). These distinctive findings are consistent with granular parakeratosis (GP). A periodic acid-Schiff (PAS) stain failed to reveal fungal hyphae. Coral fluorescence on Wood’s lamp examination, which was absent, would indicate erythrasma.

The patient was advised to discontinue or decrease frequency of antiperspirant use and prescribed topical 12% ammonium lactate lotion, but was lost to follow-up.


Axillary GP is a benign, uncommon dermatosis first recognized in 1991. It has been redesignated as simply GP after isolated lesions involving the inguinal region and other skin folds has been documented.1-3 GP has a female predominance of 25:1.4 It primarily affects middle-aged and older adults. GP is relatively rare in children and young adults although an infantile case has been described.3,5

Patients present with discrete, confluent or reticulated erythematous to brown papules and plaques in the axilla or other intertriginous areas.6 An erythematous form with reddish plaques, erosions, and occasional peripheral pustules and a hyperkeratotic form with aggregated hyperkeratotic papules and plaques admixed with verrucous papules and plaques are recognized patterns.7 Lesions may persist for weeks to months, can be unilateral or bilateral, with associated pruritus and burning. Scaliness and various degrees of maceration may be present.

Histologic examination confirms GP. GP has a distinctive pattern of cornification from which its name is derived. There is prominent compact parakeratosis within the stratum corneum with marked subjacent hypergranulosis. There may be retention of keratohyaline granules with the stratum corneum, which are prominently eosinophilic. The granular layer is thickened with focal vacuolization sometimes present.1

Although the etiology of GP is unknown, it has been suggested that it may occur secondary to contact irritants such as deodorants.Hwever, typical histological changes of an irritant contact dermatitis are not present. The contact irritant involved in GP is thought to interfere in the processing of profilaggrin to filaggrin, a protein involved in epidermal differentiation vital for normal skin barrier function.8 Disruption of this process leads to retention of nuclei in the cornified layer and aggregates of keratohyaline granules with the stratum corneum.8 Hyperhidrosis, friction, obesity, occlusive clothing, and excessive washing have also been suggested as causative factors, with lesions thought to represent a protective response to mechanical irritation.2,8

The clinical differential diagnosis for GP includes acantholytic disorders such as benign familial pemphigus (Hailey-Hailey), Darier’s Disease, and pemphigus vegetans. These all have distinct histology from GP. Pytiriasis amiantacea is a crusted and thick variant of this psoriasis on the scalp. Erythrasma causes erythema of the folds without the crusting. The constellation of histologic findings in GP is unique and specific and will confirm the diagnosis.

GP can spontaneously resolve. Management for symptomatic patients includes avoiding excessive washing and rubbing of the skin folds and minimizing the use of deodorants/antiperspirants.8 If it is persistent, oral and topical retinoids can rapidly clear GP-associated lesions within days to weeks. 8,9  Topical corticosteroids, oral/topical antifungal agents, antibiotics, cacineurin inhibitors, calcipotriene, botulinum toxin, topical ammonium lactate, and cryotherapy have shown varying degrees of success in management.8 ,10 There is, however, no agreed-upon standard-of-care therapy.


1. Northcutt AD, Nelson DM, Tschen JA. Axillary granular parakeratosis. J Am Acad Dermatol. 1991;24:541-4.

2. Mehregan DA, Thomas JE, Mehregan DR. Intertriginous granular parakeratosis. J Am Acad Dermatol. 1998;39:495-6.

3. Metze D, Rutten A. Granular parakeratosis - a unique acquired disorder of keratinization. J Cutan Pathol. 1999;26:339-52.

4. English JC, 3rd, Derdeyn AS, Wilson WM, et al. Axillary granular parakeratosis. J Cutan Med Surg. 2003;7:330-2.

5. Patrizi A, Neri I, Misciali C, et al. Granular parakeratosis: four paediatric cases. Br J Dermatol. 2002;147:1003-6.

6. Scheinfeld NS, Mones J. Granular parakeratosis: pathologic and clinical correlation of 18 cases of granular parakeratosis. J Am Acad Dermatol. 2005;52:863-7.

7. Neri I, Patrizi A, Guerrini V, et al. Granular parakeratosis in a child. Dermatology. 2003;206:177-8.

8. Channual J, Fife DJ, Wu JJ. Axillary granular parakeratosis. Cutis. 2013;92:61,5-6.

9. Laimer M, Emberger M, Brunasso AM, et al. Laser for the treatment of granular parakeratosis. Dermatol Surg. 2009;35:297-300.

10. Contreras ME, Gottfried LC, Bang RH, et al. Axillary intertriginous granular parakeratosis responsive to topical calcipotriene and ammonium lactate. Int J Dermatol. 2003;42:382-3.

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