DISCUSSION
The pathology report was consistent with axillary granular parakeratosis, a relatively rare benign disorder that manifests as unilateral or bilateral hyperpigmented erythematous scaly papules or plaques.1,2 Although most commonly found on the axilla, granular parakeratosis may also occur in other intertriginous areas.1,3 It is seen in both sexes but more commonly manifests in middle-aged women. The rash is usually asymptomatic, but mild pruritus or a burning sensation has been reported.1-4
Although the etiology is unknown, suspected causes include local irritants, such as deodorants and antiperspirants. Definitive diagnosis is made by punch biopsy. The classic histopathology demonstrates a thickened stratum corneum with retention of keratohyalin granules.1,3 Treatments include oral corticosteroids, isotretinoin, topical agents, cryotherapy, and discontinuation of underarm products.2,3 In some cases, the rash resolves spontaneously.
Folliculitis is an inflammation of the hair follicle often caused by bacteria. Obstruction of the hair follicle results in a pustular lesion. Although folliculitis may have been a consideration in this case, the clinical presentation made this diagnosis unlikely.
Acanthosis nigricans is associated with increased insulin resistance. The condition, often accompanied by obesity and diabetes mellitus, is characterized as a light brown to black velvety plaque with indiscernible margins. A lack of associated findings consistent with acanthosis nigricans made this diagnosis unlikely.
Treatment The patient decided against any further treatment. She changed her underarm deodorant and avoided wearing tight fitting clothing. At an 8-week follow-up, some resolution of the rash appeared along its outer border. JAAPA
Diana Saidac is a third-year student in the physician assistant program at Seton Hall University, South Orange, New Jersey. Denise Rizzolo is an assistant professor in the program and works at the Care Station, Springfield, New Jersey. They have indicated no relationships to disclose relating to the content of this article.
Joe R. Monroe, PA-C, MPAS, department editor
REFERENCES
1. 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.
2. Martin JM, Pinazo I, Molina I, et al. Granular parakeratosis. Int J Dermatol. 2008;47(7):707-708.
3. Barnes CJ, Lesher JL Jr, Sangueza OP. Axillary granular parakeratosis. Int J Dermatol. 2001;40(7):439-441.
4. Kossard S, White A. Axillary granular parakeratosis. Australas J Dermatol. 1998;39(3):186-187.