Granular parakeratosis – a clinical‐pathological correlation of 10 cases

BACKGROUND: Granular parakeratosis describes chronic skin lesions within the intertriginous areas that demonstrate microscopically parakeratosis together with retention of keratohyalin granules within a thickened stratum corneum. Granular parakeratosis is rarely diagnosed, since it is still relatively unknown within the differential diagnoses of intertriginous eruptions, and a skin biopsy is required for diagnosis. In order to gain insight into the clinical-histopathologic correlation, we present 10 cases of granular parakeratosis. METHODS: The files of the DermatoHistologisches Labor Dr. H. Laaff, Freiburg, were searched for the diagnosis of granular parakeratosis. Identified cases were evaluated for clinical information and histopathologic characteristics. RESULT: From 2004 to 2007 10 cases (7 women, 3 men) of granular parakeratosis were found corresponding to a frequency of 0.004%. The average age was 62 (33-82). In women lesions occurred in submammary region (4), axillae (2) and popliteal fossa; in men, groin (2) and genital region. Clinically two different patterns are recognized--lichen planus-like red-brown slightly hyperkeratotic or scaly papules, and larger plaques which are either bright red shiny or grey-brown with lichenification. Histologically the typical granular parakeratosis was seen in a prominently thickened stratum corneum. It remains unclear whether granular parakeratosis is a disease entity or whether it reflects a reaction pattern to unknown stimuli.