Infantile granular parakeratosis: cytologic examination of superficial scrapings as an aid to diagnosis.

Granular parakeratosis (GP) is a benign disorder of keratinization presenting with unilateral or bilateral red to brown hyperkeratotic plaques and papules at the intertriginous areas. The first pediatric case of GP was reported in 2002, and only a few cases have been reported since. Although the exact etiology of GP is unknown, it is thought that certain environmental factors compromise the epidermal barrier and lead to proliferation and altered maturation of the epidermis in predisposed individuals. The histopathology is diagnostic and reveals parakeratosis together with retention of keratohyalin granules within a disproportionately thickened stratum corneum and usually the preservation of stratum granulosum. Herein we report seven cases of infantile GP, six of which also had atopic dermatitis. Cytologic examination confirmed our clinical diagnosis by demonstrating the retention of keratohyalin granules and preservation of the nuclei from the superficial scrapings of the lesions, which we propose as a novel diagnostic technique. In all seven cases the lesions developed after the overuse of topical products and resolved with avoidance of their excessive use. We propose that atopic skin may be more prone to develop GP because the epidermal barrier is disrupted, resulting in the enhanced transepidermal penetration of topical products. In conclusion, GP should be included in the differential diagnosis of diaper area eruptions, especially in atopic children. Cytologic examination of superficial scrapings of the lesions can easily confirm the diagnosis of GP.