Submammary Granular Parakeratosis Treated With Mastopexy

Granular parakeratosis is a rare disorder of keratinization with a distinctive histology wherein parakeratosis with retention of keratohyaline granules is noted in the epidermis. It was first described in 1991 in a series of patients with these characteristic histopathologic features.¹ Granular parakeratosis often presents as pruritic hyperpigmented or erythematous patches and plaques in intertriginous areas,² more commonly in women than men.³ We herein report an additional case of granular parakeratosis in the submammary region. In addition, we report the electron microscopic findings in this condition. This lesion is strongly associated with, and most likely caused by, heat and friction, and indeed improves with treatment addressing those entities. We believe this is a reactive, protective phenomenon to heat, moisture, and friction.

A 36-year old white female presented with an 18-month history of an intermittent asymptomatic but “unsightly” eruption of the inframammary area, aggravated by perspiration and physical activity (Figure 1). Physical examination revealed approximately 40 bilateral inframammary papules and plaques. They were discrete, light brown, keratotic, and flat topped, with a focally circinate appearance. Potassium hydroxide (KOH) preparation was repeatedly negative. No significant improvement was noted with a variety of topical creams; only non-medicated powder provided transient relief. However, after elective mammopexy, the lesions completely resolved. Of note, the patient reports that her biological mother and sister exhibit similar lesions.

Paraffin-embedded, H&E-stained sections of a punch biopsy were examined and demonstrated slight acanthosis, and a sparse superficial perivascular dermal lymphocytic infiltrate. The most striking feature was marked thickening of the stratum corneum, which was hypereosinophilic. There was retention of both keratohyaline granules and keratinocyte nuclei throughout its thickness (Figure 2). In addition, electron microscopy was performed on one-half of the punch biopsy. As the keratinocytes transition to the stratum corneum, they demonstrate pyknotic nuclei, numerous keratohyaline granules, and membrane-coating granules (Odland bodies). The keratohyaline granules were normal in size and appearance in the granular layer. Instead of the expected dissolution, they were retained throughout the thickness of the stratum corneum, and appeared somewhat rounded and irregular in shape compared to the granular layer (Figure 3).

Intertriginous granular parakeratosis is an uncommon disease of unknown etiology. Originally described as “axillary granular parakeratosis”, it was hypothesized to be due to a contact irritant, perhaps contained in antiperspirant or deodorant because of axillary predilection.¹ Friction, heat, and moisture were then proposed as etiologic factors with the additional demonstration of groin involvement.⁴ Subsequent cases have been demonstrated in the submammary region, abdominal folds, and perianal region.^4-6 The current demonstration of a case in the inframammary region strengthens this causative hypothesis of friction, heat, and moisture.The pathogensis of granular parakeratosis has been proposed to be a defect in processing filaggrin; this results in failure of keratohyaline granule degradation.⁵ The failure of degradation of keratohyaline granules and keratinosomes upon epidermal maturation, here convincingly illustrated by electron microscopy, has not been described in any other inflammatory process (Figure 3). Under normal low-moisture conditions, these structures undergo degradation. It is unlikely coincidental that the contents of these structures are believed to protect the host from extrinsic moisture. The maintenance of these structures is