Scaly erythematous eruptions of intertriginous locations

Intertriginous eruptions are common presenting problems in clinical practice and include several diagnoses. A good history with a thorough evaluation of rash guides a proper management. A biopsy may be required in cases of clinical ambiguity. We here present a case of scaly erythematous eruptions in a female adult, leading a diagnosis of granular parakeratosis.    

Case report

A female in her late twenties presented with a 6-week history of persistent erythematous patches and plaques with desquamation, scales and wrinkled appearance, involving the intertriginous areas (Figure 1). She had no known allergies or significant medical history and was taking no medications. As a result of COVID-19 precautions she had recently begun using a laundry detergent containing benzalkonium chloride (BAC). She had been treated with mid-strength topical corticosteroid with a limited response. On examination, she was Fitzpatrick skin type 2, afebrile and systemically well, apart from symmetrical reddish-brown scaly papules, patches and plaques involving the groin, gluteal fold, axilla, inframammary fold, and mid-back (under bra) (Figure 1).

Discussion

The differential diagnoses of an intertriginous eruption are listed in Table 1, with related characteristic features.^1–3 In this case no fungal pathogens were found on microscopy; immunoglobulin E level was within normal range, and HIV and syphilis serology were negative. Histopathology from biopsy was reported as demonstrating hyperkeratosis, parakeratosis and hypergranulosis, typical of granular parakeratosis.

Granular parakeratosis, also known as hyperkeratotic flexural erythema, is an intermittently encountered reddish-brown intertriginous dermatosis with occasional involvement of non-intertriginous areas (e.g., mid-back under bra). It was first described in 1991 by Northcutt et al. in the axillary region.⁴ Aetiopathogenesis of granular parakeratosis remains speculative with exposure to BAC (an antimicrobial preservative that is found in a number of household products including detergents, antiseptics and skincare products) or other irritants, in combination with occlusive, pressured and frictional locations of susceptible individuals.^1,3 There is no reported sex or age predilection; however, more adult female cases have been reported in the literature.^3,5,6 Although no standardised treatment for granular parakeratosis exists, management includes the avoidance of inciting triggers, general skincare and the use of topical and systemic agents such as corticosteroids, retinoids, vitamin D analogues, antibiotics and phototherapy or laser.^5,6 This case was treated with betamethasone dipropionate 0.05% ointment with emollients and avoidance of BAC, with resolution in 4 weeks. It has also been reported that spontaneous clearing of granular parakeratosis can also occur between months and year.^1,7

View Figure 1 and Table 1.

‍