CASE #1

The patient, a 45-year-old woman, was concerned about an eruption of scaly erythematous papules that had developed in both axillae three to four months earlier. Although the lesions were asymptomatic, the patient was concerned about their unsightly appearance. The woman regularly used deodorant and had not recently switched brands. In generally good health, she was not taking any medications and had no similar lesions.

CASE #2

An otherwise healthy 35-year-old African-American man had a two-week history of purple oval papules and plaques in his axillae and a single, large 3-cm plaque on his back. The lesions were slightly to moderately pruritic. He had not recently changed deodorants, soaps, or detergents. Neither tinea nor candidal infection was detected on KOH preparation. Rapid plasma reagin (RPR) and antistreptolysin-O (ASLO) tests were negative.

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Diagnosis: Axillary granular parakeratosis

The woman had axillary granular parakeratosis (GP), a benign condition. First described in 1991, this disease presents with erythematous hyperpigmented and hyperkeratotic papules and plaques in cutaneous folds. In addition to the axillae, intertriginous forms of the disease can develop in the groin, intermammary or submammary region, and abdominal folds. Associated pruritus may develop.

Although the exact cause of axillary GP is unknown, its origin has been linked to excessive use of topical preparations, in particular antiperspirants and deodorants; however, axillary GP has also been found in persons who have not used such agents. Axillary GP is associated with an occlusive environment, increased sweating, and, less frequently, local irritation. Some studies have linked the condition to obesity. 

GP is rare. In a dermatopathology laboratory, during a five-year period, 18 of 363,343 specimens (0.005%) were diagnosed as GP. All of the specimens were taken from the axillae of adult patients; the majority were women. Most patients who present with suspected GP will have a one- to 12-month history of axillary or intertriginous rash. The condition manifests with intertriginous, bilateral or unilateral, brown- or red-crusted patches, papules, or plaques. GP can be confluent or reticulated. Even when patches or plaques are present, discrete papules can also be seen. Slightly erythematous and lichenified plaques have been reported as well. 

In children, GP has been observed in the groin and on the lower back, buttocks, and flanks. 

The differential diagnosis includes acanthosis nigricans, intertrigo, confluent and reticulated papillomatosis, erythrasma, extramammary Paget's disease, inverse psoriasis, inverse lichen planus, inverse pityriasis rosea, pemphigus vegetans, and benign familial pemphigus. GP is best distinguished from intertrigo by the presence of dry or keratotic scale in areas where maceration is the usual manifestation of an eruption. 

When GP is suspected, evaluation should include a KOH preparation to check for causative fungi or yeast. Examination with a Wood's lamp will rule out erythrasma. Definitive diagnosis is made on biopsy. Characteristic histologic findings include psoriasiform hyperplasia, a thickened stratum corneum with retention of keratohyalin granules, parakeratosis, a well-developed granular layer, and a sparse lymphohistiocytic inflammatory infiltrate. The retained granular layer can show focal vacuolization.

Effective treatments include topical steroids, pimecrolimus cream, topical retinoids, topical calcipotriene, and ammonium lactate. Prognosis is good with any form of treatment and avoidance of inciting factors. Sometimes GP resists treatment and has a chronic and relapsing course.

Our patient was treated with desonide 0.05% lotion. Her eruption resolved in one month. One year later, the eruption had not recurred.

Diagnosis: Inverse pityriasis rosea

This patient had pityriasis rosea, an acute inflammatory dermatosis of unknown etiology. Viruses, particularly human herpesvirus 6 and 7, have been suggested as the causative pathogen, but study results have not been definitive.

Pityriasis rosea is common among Americans, with more than 5% of the U.S. population affected. Gender prevalence is a 1.5:1 ratio of females to males. Patients are typically children and young adults, with incidence peaking during the second decade. In a study of patients in Minnesota, 75% were between 10 and 35 years of age (range 10 months to 78 years; mean age 22.7).1 Cases occur most frequently during the spring, but lesions can develop during any time of the year. 

Presentation of pityriasis rosea follows a classic natural history. Commonly, a single large plaque appears on the scapular area. The characteristic herald lesion is usually red or brown and bordered by a fine scale. This is followed by development of smaller oval lesions along Langer's lines. On the back, the lesions develop in a “Christmas tree” pattern. On other areas, they follow the cleavage lines, i.e., transversely across the abdomen, around the shoulders, and in a V-shaped pattern on the chest. Inverse disease occurs when the extremities or intertriginous areas are affected but the trunk is spared. Eruptions normally last five to eight weeks; however, 25% of cases last for up to 12 weeks. Pruritus is found in 75% of cases; one quarter of these are severe. 

A number of conditions can be confused with pityriasis rosea, including guttate psoriasis, erythema annulare centrifugum, secondary syphilis, nummular dermatitis, drug eruptions (particularly reactions to heavy metals, most commonly gold), Gianotti-Crosti syndrome, tinea corporis, pityriasis lichenoides parapsoriasis, and cutaneous lupus. Diagnosis is usually clinical and does not require biopsy. An RPR test should be done to rule out syphilis. Guttate psoriasis patients will have an elevated ASLO. Tinea is ruled out by absence of hyphae on a KOH preparation. 

Inverse pityriasis is rare. In one study of 368 patients with pityriasis rosea, inverse distribution involving mainly the extremities was seen in 22 cases (6%).2 A second study of 50 affected patients found inverse disease in 2% of cases.3 The differential diagnosis of inverse pityriasis rosea includes inverse psoriasis, inverse lichen planus, intertrigo, axillary granular parakeratosis, variants of pemphigus, Hailey-Hailey disease, Darier's disease, and candidiasis. No difference in morbidity or disease outcome has been observed between the inverse and the usual distributions.

Because pityriasis rosea is self-limiting, the role of treatment is unclear. Therapy is typically initiated to eliminate associated pruritus, with oral antihistamines and topical corticosteroids most frequently used. 

In one prospective, blinded, placebo-controlled study of 90 patients, complete clearance of lesions was seen in 73% of those who received a two-week course of erythromycin four times daily.4 In the same study, no clearance was seen in those who received placebo. The effect of erythromycin may be linked to its anti-inflammatory properties. Reports have also suggested that acyclovir (800 mg five times daily) can shorten disease duration. In one series, azithromycin was no better than placebo in shortening duration of pityriasis rosea in children. Severe disease may be treated with phototherapy. Recurrence is seen in 1.8% of patients after an average 4.5 years of follow-up.1 In patients of color, cleared lesions can leave behind dark brown macules. 

Our patient was prescribed azithromycin (Zithromax) 500 mg for one day and 250 mg for four days. Tacrolimus (0.1%) ointment (Protopic) was to be applied twice daily to the axillae. Eight weeks later, the eruption had resolved.    

Dr. Scheinfeld is chief of pediatric dermatology and chief of clinical trials in the Department of Dermatology at Metropolitan Hospital/New York Medical College in New York City and assistant clinical professor of dermatology at Columbia University, also in New York City.

References

1. Chuang TY, Ilstrup DM, Perry HO, Kurland LT. Pityriasis rosea in Rochester, Minnesota, 1969 to 1978. J Am Acad Dermatol. 1982;7:80-89.
2. Tay YK, Goh CL. One-year review of pityriasis rosea at the National Skin Centre, Singapore. Ann Acad Med Singapore. 1999;28:829-831.
3. Egwin AS, Martis J, Bhat RM, et al. A clinical study on pityriasis rosea. Indian J Dermatol. 2005;50:136-138.
4. Sharma PK, Yadav TP, Gautam RK, et al. Erythromycin in pityriasis rosea: a double-blind, placebo-controlled clinical trial. J Am Acad Dermatol. 2000;42 (2 pt 1):241-244.