DP16 Trichilemmocysticus naevus: a rare birthmark treated successfully with erbium ablative laser

• Published in: British journal of dermatology (1951) 2023-06, Vol.188 (Supplement_4)
• Main Authors: Bennett, Hannah, Urwin, Rachel, Merchant, Will
• Format: Article
• Language: English
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1093/bjd/ljad113.229

We report a rare case of a 58-year-old woman with a naevus trichilemmocysticus. The patient presented to a tertiary dermatology centre with longstanding skin changes to her trunk. The changes had been apparent since childhood and became more prominent in her teens. Examination showed a linear Blaschkoid distribution of subtle hyperpigmentation and warty follicular prominence to the left submammary region, extending to the left upper back, where comedones and cystic papules were also noted. Histopathology confirmed the presence of cysts containing keratin, lined by trichilemmal-type squamous epithelium, representing trichilemmal cysts. The overlying epidermis appeared normal. Given the Blaschkoid distribution and the presence since childhood, it was thought that this most likely represented a naevus trichilemmocysticus. Tantcheva-Poor et al. described and named this as a rare type of organoid naevus-type lesion in 2007 (Tantcheva-Poor I, Reinhold K, Krieg T, Happle R. Trichilemmal cyst nevus: a new complex organoid epidermal nevus. J Am Acad Dermatol 2007; 57:S72–7). Only seven cases have been identified and reported in the literature. These have been characterized by multiple follicular filiform hyperkeratoses and trichilemmal cysts in a Blaschkoid distribution. Most cases described involve extensive areas of the skin and present with disfiguring lesions. Histology reports confirm epidermal acanthosis with deep invaginations filled with massive orthokeratosis, parakeratotic columns and an absent granular layer (isthmic or trichilemmal differentiation) with keratosis in sebaceous ducts and acrosyringia. Our patient is currently undergoing successful treatment with erbium laser under local anaesthesia, in order to improve the texture and appearance of the birthmark. This has been achieved by ablation to the warty areas to the level of upper papillary dermis, with focal deeper ablation to the skin overlying each cyst, followed by the use of a meibomian cyst curette for enucleation.