Cup-shaped itchy papule

Question

What’s the diagnosis?

Answer

Diagnosis: Warty dyskeratoma

Discussion

Warty dyskeratoma (WD), first reported by Szymanski, is a rare benign tumour mostly presenting as a solitary papule or nodule with a central, depressed, crater-like pore over the head and neck region. Rare presentations include involvement of extra craniofacial sites, mucosae and multiple lesions.^1,2 WD exhibits a sporadic focal failure of epithelial maturation, demonstrating acantholytic dyskeratosis without germline mutations in ATP2A2. The exact pathogenesis is multifactorial and still unclear.³ Hair-bearing areas are most commonly affected; solitary papule or nodule being the commonest presentation. Predilection for the head and neck region, early lesions being associated with sebaceous glands, serial sections showing attachment to the follicular unit in previous studies, and expression of human keratin monoclonal antibodies HKN-6 and -7 are suggestive of a follicular-origin tumour.^1,4 However, mucosal lesions that do not show follicular origin on immunostaining, contradict this theory. Other possible etiologies include human papillomavirus (HPV) infection, ultraviolet light, and tobacco. However, a large study failed to demonstrate HPV-DNA on PCR assessment.³ WD is a benign, slow-growing tumour that always remains asymptomatic. However, pruritus has been reported, attributed to eosinophilic infiltration, though this was absent in our case.

Focal acantholytic dyskeratosis is also present in Darier’s disease, Hailey-Hailey disease, transient acantholytic dyskeratosis (Grover’s disease), acantholytic dermatosis of the vulvocrural area, actinic keratosis, acantholytic squamous cell carcinoma (SCC), and linear epidermal naevus. However, the characteristic cup-shaped histomorphology and the clinical features are hallmarks of WD.

In our case, dermoscopy showed a central reddish stellate crust on an erythematous background, indicating the crater with underlying vascular structures. The central crust on dermoscopy and histologic evidence of neutrophils likely reflect secondary changes due to chronic pruritus and excoriation. The surrounding white radial streaks and peripheral hyperpigmentation likely reflect the acanthotic epidermis and pruritus-related changes, respectively. The dermoscopy in our patient varies from the previously reported “coarse cobblestone pattern” and “jellyfish-like pattern,” likely due to associated pruritus and secondary erosion in our case. The clinical differentials include verruca vulgaris, seborrheic keratoses, keratoacanthoma, and folliculitis. Our patient was diagnosed with folliculitis and lichen simplex chronicus previously and underwent unsuccessful treatment with topical and systemic antibiotics. Histologically, three architectural patterns are reported, including cup-shaped, cystic, nodular, and their combinations. Treatment for solitary WD is typically surgical. For multiple WDs, proposed treatments include ablative laser therapy and topical retinoids.⁵