CLINICAL HISTORY:

Signs and symptoms:  A 71 year old Hispanic female with a past medical history of insulin dependent diabetes, and left cerebral vascular accident was referred by her primary care physician for evaluation of a unilateral, hyperpigmented rash located in the right axilla. According to the patient the rash had been present for three weeks. She admitted to using copious amounts of deodorants in the area. The patient denied any symptoms of pruitus or burning.

Previous Treatment:  Prior to presentation, she did not receive any treatment for her rash.

Other information: 

PHYSICAL EXAM:

Cutaneous examination revealed multiple hyperpigmented papules coalescing into a velvety plaque in a linear distribution in the right axilla. No active lesions were noted in the left axilla. Due to her past history of a left sided stroke, the patient was noted to have difficulty raising her right axilla.

LABORATORY TESTS:

A 3-mm punch biopsy of a right axillary lesion was performed. The patient was asked to discontinue deodorant use and replaced it with bacitracin ointment bid to the biopsy site.

DERMATOHISTOPATHOLOGY:

Microscopic evaluation revealed severe compact parakeratosis with retention of keratohyalin granules throughout the stratum corneum.

DIFFERENTIAL DIAGNOSIS:

1.   unilateral acanthosis nigricans
2.   axillary granular parakeratosis
3.   post-inflammatory hyperpigmentation
4.   linear epidermal nevi
5.   contact dermatitis

SCROLL DOWN FOR ANSWER AND DISCUSSION.

CORRECT DIAGNOSIS:

Axillary granular parakeratosis

DISCUSSION:

Axillary granular parakeratosis was first described by Northcutt et al in 1991. The exact etiology is not known. Most of the case reports have reported an excessive and recurrent exogenous topical stimuli (deodorants, antiperspirants, shampoos, bath soaps) in body folds (axilla, submammary regions). Authors suggest that an irritation of the keratinocytes in the upper stratum granulosum occurs and leads to altered differentiation with persistence of the keratohyalin granules, clinically, corresponding to hyperkeratotic papules. Others believe that there is an underlying disorder of cornification.

Due to the patient’s presentation of a unilateral axillary rash on the affected side of her stroke our case further supports the theory of excessive deodorant use in occlusive environment leading to granular parakeratosis.

TREATMENT:

Treatment usually entails discontinuation of the offending agent. However, the use of retinoids has been reported. The lesion usually resolves completely without further sequela.

REFERENCES:

Northcutt AD, Nelson DM, et al. Axillary granular parakeratosis. JAAD.1999; 24(4):541-4

Mehregan DA, Vandersteen P, Sikorski L, Mehregan DR. Axillary granular parakeratosis. JAAD. 1995;33(2 pt2):373-5.

Wohlrab J et al. Submammary granular parakeratosis: an acquired punctate hyperkeratosis of exogenic origin. JAAD. 1999;40(5pt2):813-4

Metze D et al. Granular parakeratosis- a unique acquired disorder of keratinization. J of Cutaneous Pathology. 1999;26(7):339-52.

Kossard S et al Axillary granular parakeratosis. Australian J of Derm 1998;39(3):186-7.

Webster CG et al. Axillary granular parakertosis: response to isotretinoin. JAAD 1997. 37(5pt1):789-90

Additional Comment:

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