What Are the Scaly Reddish Lesions in This Woman’s Armpits?
A 40-year-old obese white woman presented with scaly, brownish eruptions in both axillae of approximately 8 months’ duration. The lesions had started as small brownish papules that over time had slowly increased in size and had coalesced to form plaques. The lesions were odorless and asymptomatic. She had atopic dermatitis but was otherwise in good health. She was not on any medications. She did not recall any change in soap or detergent or any change in her deodorant. There was no family history of similar skin lesions.
The physical examination revealed 2 well-demarcated, linear, reddish brown, scaly, crusted hyperkeratotic plaques, 1 on each axillary area. Her height was 154 cm, her weight was 70 kg, and her body mass index was 29.5 kg/m2 (normal value, < 25 kg/m2). The rest of the physical examination findings were normal. In particular, there was no involvement of other intertriginous sites.
What’s Your Diagnosis?
B. Acanthosis nigricans
C. Axillary granular parakeratosis
D. Confluent and reticulated papillomatosis
Answer and discussion on next page.
Answer: Axillary granular parakeratosis
Axillary granular parakeratosis is a benign disorder of keratinization characterized clinically by erythematous to brown hyperpigmented and hyperkeratotic papules/plaques in the axillary area and histologically by hyperkeratosis, parakeratosis, and retention of keratohyaline granules in the stratum corneum.1 The condition was first described in 1991 by Northcutt and colleagues,2 who reported on 5 patients with this kind of axillary eruptions, all with a histologically distinctive granular appearance of the parakeratotic horny layer. The term axillary granular parakeratosis was coined by these authors.
Axillary granular parakeratosis is a rare condition, although the exact prevalence is not known. Scheinfeld and Mones3 reviewed the diagnosis of 363,343 specimens submitted to the Ackerman Academy of Dermatopathology in New York between July 1, 1999, and December 31, 2003. Eighteen (0.005%) specimens were diagnosed with granular parakeratosis. The condition most commonly is observed in individuals between 40 and 50 years of age,1 although children also can be affected.4 The female-to-male ratio is between approximately 5 to 1 and 25 to 1.3,5,6 There is no known predilection for race or ethnicity.
The exact etiopathogenesis is not known. Some authors believe that granular parakeratosis results from a basic defect in processing profilaggrin to filaggrin, resulting in a failure to degrade keratohyaline granules.2 Other authors suggest that the condition is an allergic contact or irritant reaction.4,5,7 The use of antiperspirants and deodorants has been implicated.2,8 Other predisposing factors include genetic predisposition, obesity, atopic dermatitis, occlusive environment, friction, and hyperhidrosis.3-5
Histologic features include hyperkeratosis, compact parakeratosis, acanthosis, papillomatosis, and retention of basophilic keratohyaline granules within a thickened stratum corneum, often with a perivascular infiltrate consisting of lymphocytes and histiocytes.1,3-5 The granular appearance of the stratum corneum is due to the retention of basophilic keratohyaline granules, hence its name.
Initially, the lesions present as small, reddish-brown keratotic papules in the axillae.1 These papules can coalesce to form crusted, hyperkeratotic, well-demarcated plaques, with a cobblestone “stuck-on” appearance.8,9 The lesions may be discrete, confluent, or reticulated. The plaques may be covered by scale or crust, and satellite papules also may be present.1,5 The condition may be unilateral or bilateral.9,10 The lesions usually are asymptomatic but at times may be pruritic, painful, or burning.1
DIAGNOSIS AND LABORATORY INVESTIGATIONS
The diagnosis often can be made clinically. A Wood lamp can be used to rule out erythrasma. A potassium hydroxide wet-mount examination of skin scrapings can be performed to rule out a fungal infection. Cytologic examination of superficial scrapings from the lesion can be used to demonstrate retention of keratohyaline granules and preservation of cell nuclei within stratum corneum keratinocytes.4 Referral to a dermatologist should be considered if the diagnosis is in doubt. Histologic examination is required for definitive diagnosis.
The differential diagnosis includes acanthosis nigricans, intertrigo, erythrasma, contact dermatitis, confluent and reticulated papillomatosis, fungal infection, nummular eczema, granuloma annulare, linear epidermal nevus, seborrheic keratosis, verruca plana, inverse lichen planus, inverse psoriasis, pemphigus vulgaris, pemphigus vegetans, Hailey-Hailey disease, Bowen disease, Darier disease, and Dowling-Degos disease.1,4,10
Axillary granular parakeratosis does not lead to any systemic disease. However, it can be cosmetically and socially embarrassing.
Although the condition may run a chronic and relapsing course, it also may resolve on its own.1,9
Underlying causes such as obesity should be treated if possible. For patients who desire treatment for cosmetic or symptomatic reasons, treatment options include topical corticosteroids, topical calcineurin inhibitors (tacrolimus, pimecrolimus), topical retinoids (tretinoin, tazarotene), topical vitamin D3 analogues (calcipotriol, calcipotriene), topical keratolytics (lactic acid, salicylic acid, urea), topical ammonium lactate, oral retinoids (isotretinoin, acitretin), cryotherapy, botulinum toxin injections, or ablative lasers.1,9,10 Individual cases have responded to a variety of these treatment modalities. However, there is no optimal treatment for this condition, and there have been no controlled trials.
Alexander K. C. Leung, MD, is clinical professor of pediatrics at the University of Calgary and a pediatric consultant at the Alberta Children’s Hospital in Calgary, Alberta, Canada.
Benjamin Barankin, MD, is a dermatologist and the medical director and founder of the Toronto Dermatology Centre in Toronto, Ontario, Canada.
- Ding CY, Liu H, Khachemoune A. Granular parakeratosis: a comprehensive review and a critical reappraisal. Am J Clin Dermatol. 2015;16(6):495-500.
- Northcutt AD, Nelson DM, Tschen JA. Axillary granular parakeratosis. J Am Acad Dermatol. 1991;24(4):541-544.
- Scheinfeld NS, Mones J. Granular parakeratosis: pathologic and clinical correlation of 18 cases of granular parakeratosis. J Am Acad Dermatol. 2005;52(5):863-867.
- Akkaya AD, Oram Y, Aydın Ö. Infantile granular parakeratosis: cytologic examination of superficial scrapings as an aid to diagnosis. Pediatr Dermatol. 2015;32(3):392-396.
- Channual J, Fife DJ, Wu JJ. Axillary granular parakeratosis. Cutis. 2013;92(2):61, 65-66.
- English JC 3rd, Derdeyn AS, Wilson WM, Patterson JW. Axillary granular parakeratosis. J Cutan Med Surg. 2003;7(4):330-332.
- Wallace CA, Pichardo RO, Yosipovitch G, Hancox J, Sangueza OP. Granular parakeratosis: a case report and literature review. J Cutan Pathol. 2003;30(5):332-335.
- Urbina F, Sudy E, Misad C. Two episodes of axillary granular parakeratosis triggered by different causes: case report. Acta Dermatovenerol Croat. 2012;20(2):105-107.
- Samrao A, Reis M, Niedt G, Rudikoff D. Granular parakeratosis: response to calcipotriene and brief review of current therapeutic options. Skinmed. 2010;8(6):357-359.
- Ravitskiy L, Heymann WR. Botulinum toxin-induced resolution of axillary granular parakeratosis. Skinmed. 2005;4(2):118-120.