Granular Parakeratosis

Etiology

Granular parakeratosis was first described in the axillae and subsequently described to involve other intertriginous areas.[7][6] The condition was originally thought to be a contact dermatitis to personal hygiene products such as deodorants and antiperspirants; however, cases have been reported in the absence of personal hygiene products in the affected areas, which discredited contact dermatitis as the etiology.[1] The possibility of the condition being an unusual reaction to other topical preparations has not been entirely ruled out as a contributing etiology. Occlusion does appear to be a factor in the etiology of granular parakeratosis, given the predilection for intertriginous areas. Case reports have also noted the resolution of lesions of granular parakeratosis following the elimination of occlusion.[8] Case reports have also noted granular parakeratosis in non-intertriginous body areas such as the face, so occlusion does not appear to be the only etiologic factor.[4][5] Infectious etiologies, such as bacterial or fungal, have had inadequate microbial cultures to support it as an etiology; however, there have been case reports of response to oral antibiotics such as amoxicillin-clavulanate.[9] Given the inconsistent response to various treatments and lack of consistent clinical evidence or patient history, granular parakeratosis is classified as an idiopathic condition.

Epidemiology

Granular parakeratosis has been reported in all ages but is most commonly seen in adults. The condition has a higher prevalence amongst women than men. Granular parakeratosis does not appear to have a geographical or racial predilection. The condition is rare with one study reporting granular parakeratosis being present in only 18 specimens among 363,343 specimens examined.[2] Granular parakeratosis is thought, by some, to be associated with obesity due to the condition being most often reported within intertriginous and occluded body areas.[10] Granular parakeratosis has not been associated with any systemic diseases.

Histopathology

Granular parakeratosis is a rare, benign, idiopathic condition that is best categorized as a reaction pattern rather than a distinct disease. The diagnosis of granular parakeratosis is made by histopathologic evaluation. A punch or shave biopsy should be completed for diagnosis. The confirmation of granular parakeratosis on hematoxylin and eosin (H&E) staining is adequate to confirm the diagnosis. On biopsy, a thickened stratum corneum is noted with abnormal retention of keratohyalin granules as well as an intact stratum granulosum.[2] A biopsy can also delineate if granular parakeratosis is present as a separate reaction pattern or concomitantly present with other treatable conditions such as tinea corporis. On electron microscopy, granular parakeratosis presents as round or stellate keratohyalin granules within the granular layer and retained keratohyalin granules within the corneocytes of the stratum corneum.[11]

History and Physical

Patients with granular parakeratosis typically present with asymptomatic to pruritic papules or plaques in intertriginous areas. Granular parakeratosis can arise over several days to months and presents in areas of previously normal skin.[1] The lesions are typically reddish to brown and present as scaly to keratotic papules that may coalesce into plaques. In adults, granular parakeratosis typically presents in intertriginous areas such as the axillae, submammary folds, abdominal folds, or inguinal folds. In children, two main presenting patterns have been identified. The first clinical pattern described in children presents as linear plaques in the bilateral inguinal folds with a flaky scale. The second pattern described in children presents as geometric plaques in areas of increased pressure during diaper-wearing. Occlusion from diapers does appear to contribute to the presentation of granular parakeratosis in infants; however, the pathogenesis is not clear.[12]

Evaluation

Granular parakeratosis clinically may be confused with several other conditions such as Hailey-Hailey disease, verruca, contact dermatitis, acanthosis nigricans, erythrasma, confluent and reticulated papillomatosis, extramammary Paget disease, amongst others. Granular parakeratosis has also been found to be present concomitantly with other conditions such as tinea corporis. Thus, a punch or shave biopsy should be completed for histopathologic evaluation. The confirmation of granular parakeratosis on hematoxylin and eosin (H&E) staining is adequate to confirm the diagnosis. On biopsy, a thickened stratum corneum is noted with abnormal retention of keratohyalin granules as well as an intact stratum granulosum.[2] A biopsy can also delineate if granular parakeratosis is present as a separate reaction pattern or concomitantly present with other treatable conditions such as tinea corporis.

Treatment / Management

Multiple treatments have been attempted for granular parakeratosis; however, responses to these treatments have been inconsistent amongst reported cases. Given previous thoughts that granular parakeratosis may be an abnormal reaction to personal hygiene products or other topical preparations, discontinuing these topicals as well as prescribing a topical steroid is typically the first attempted management strategy. Topical steroids may decrease pruritus in symptomatic patients; however, reported cases have rarely resolved with topical steroids as monotherapy.[3] One case report noted complete resolution of axillary granular parakeratosis with five days of topical tretinoin 0.025% cream.[1] Another case report noted complete resolution of axillary granular parakeratosis with 10 days of topical calcitriol ointment.[13] Granular parakeratosis has also been reported to respond rapidly to oral isotretinoin in one case report.[14] There has also been one case report of surgical management of submammary granular parakeratosis with elective mastopexy resulting in complete resolution.[8](B3)

Differential Diagnosis

• Hailey-Hailey disease
• Verruca
• Contact dermatitis
• Acanthosis nigricans
• Erythrasma
• Confluent and reticulated papillomatosis
• Extramammary Paget disease
• Inverse psoriasis
• Pemphigus veterans
• Bowen disease

Prognosis

Granular parakeratosis most often is self-limiting and will resolve in a period of one month to one year.[2][6] However, cases have been reported of granular parakeratosis persisting or chronically recurring for up to 20 years.[15] The condition is not associated with malignancy or any systemic diseases. Obesity and increased occlusion of skin-folds do appear to contribute to granular parakeratosis.

Complications

There have been no reported cases of malignant transformation of granular parakeratosis. Patients with granular parakeratosis may develop secondary overlying bacterial infections, especially in patients with symptomatic pruritic lesions that become impetiginized with scratching. Granular parakeratosis has been found to be concomitantly present with other common skin conditions such as tinea corporis.[2]