Porokeratotic Eccrine Ostial and Dermal Duct Nevus: A Report of Rare Late-Onset Solitary Lesion

Introduction

Porokeratotic eccrine ostial and dermal duct nevus (PEODDN), first described by Marsden et al in 1979 as “comedo nevus”, is a disorder of abnormal keratinization in the eccrine sweat gland, specifically over the dilated acrosyringium.^1,2 The term was later changed to “PEODDN” to better reflect its histopathological features.³ While typically congenital or early childhood onset involving multiple, linearly distributed, hyperkeratotic papules predominantly affecting the palms and soles, rare cases of adult-onset PEODDN and solitary lesion have been reported, highlighting the variable clinical spectrum of this condition. The definitive diagnosis of PEODDN relies on the histopathological hallmark of the cornoid lamella overlying dilated eccrine acrosyringia.³

The etiology of PEODDN remains unclear. However, recent genetic studies have provided valuable insights into its pathogenesis, with implications for both diagnostic and therapeutic approaches. Herein, we present an atypical case of late-onset solitary PEODDN in a 64-year-old woman. By describing this unusual presentation and providing a comprehensive review of the literature, we aimed to enhance our understanding of the clinical variability of PEODDN and guide clinicians in its diagnosis and management.

Case Presentation

A 64-year-old woman presented with a solitary nodule on the medial side of her left foot that had been present for three months. The patient reported that the lesion had gradually increased in size, but remained asymptomatic throughout this period. The medical history included asthma and systemic sclerosis with interstitial lung fibrosis. The patient was under regular follow-up with a rheumatologist and a pulmonologist, and her condition was stable. The patient denied having a family history of similar skin lesions or other hereditary skin conditions. Physical examination revealed a solitary, well-demarcated, brownish hyperkeratotic papule on the left foot (Figure 1A). The lesion had a slight verrucous surface with central scaling (Figure 1B). There were no signs of inflammation, and no similar lesions were found elsewhere in the body. According to the presentation, the differential diagnoses included verruca vulgaris, prurigo nodularis, dermatofibroma, eccrine poroma, and basal cell carcinoma.

Figure 1 Clinical presentation: (A) solitary, well-demarcated, brownish, hyperkeratotic papule; (B) close-up picture showing slightly verrucous surface with central scaling.

Given the atypical presentation and location of the lesion, punch biopsy was performed for diagnosis. Histopathological examination revealed a vertical column of parakeratosis overlying a dilated acrosyringium, consistent with a cornoid lamella (Figure 2A). The epidermis exhibited dwellings, absence of a subjacent granular layer, and perinuclear halos (Figure 2B). The underlying dermis and subcutis were both normal. These histopathological features were consistent with those observed in PEODDN. Based on the clinical presentation and histopathological findings, late-onset solitary PEODDN was diagnosed. After discussing the treatment options with the patient, we decided to proceed with CO₂ laser therapy because of its reported efficacy in previous cases of PEODDN and the localized nature of the lesion. At the one-month follow-up visit, the treated area healed well, with minimal residual erythema and no evidence of recurrence. The patient reported satisfaction with cosmetic outcomes.

Figure 2 Histopathological features (hematoxylin-eosin staining): (A) vertical column of parakeratosis overlying dilated acrosyringium (arrow), forming characteristic cornoid lamella (original magnification x100); (B) epidermal dwelling with absence of granular layer (original magnification x400).

Discussion

Our case presents unique features that contribute to the existing literature on PEODDN. First, late onset at 64 years of age is unusual because PEODDN typically presents in early childhood or is congenital. Second, the solitary nature of the lesion contrasts with the more common linear or systematized distribution along the Blaschko lines. To identify previous reports of solitary PEODDN, we conducted a comprehensive literature search using PubMed and Scopus databases from inception to December 2024. The search terms included “porokeratotic eccrine ostial and dermal duct nevus”, “PEODDN”, “eccrine nevus”, “porokeratotic adnexal ostial nevus”, “comedo nevus”, “solitary”, and “adult-onset”. Additional references were identified through manual searches of the reference lists of relevant articles. This search strategy identified only three previously reported cases of adult-onset solitary PEODDN, as summarized in Table 1.^4–6

Table 1 Previously Reported Cases of Porokeratotic Eccrine Ostial and Dermal Duct Nevus Presenting With Solitary Lesion

The exact prevalence of PEODDN remains unknown, further emphasizing its uncommon nature. The rarity of PEODDN is evident in the limited number of reported cases. To date, fewer than 100 cases have been documented in the literature, making it a challenging condition to diagnose and manage.⁵ The majority of cases present with multiple erythematous yellowish keratotic papules with central pits or verrucous-like lesions distributed along the Blaschko lines. The lesions are generally asymptomatic, but mild to moderate itching or intermittent inflammation can occur.⁷ PEODDN shows no gender predilection and is typically congenital or of childhood onset.⁵ The disease is primarily unilateral and predominantly involves the palms and soles, although generalized involvement of proximal extremities and trunk has been reported.^8–11 Definitive diagnosis of the disease is made according to histopathological characteristics of parakeratotic column of cornoid lamellae overlying dilated or hyperplastic eccrine acrosyringia with subjacent granular layer loss, focal vacuolization of adjacent keratinocyte, and occasionally sparse lymphocytic infiltration.⁵

It is crucial to differentiate PEODDN from entities with similar clinical presentations, particularly those with malignant potential. Eccrine porocarcinoma is an important differential diagnosis that warrants special attention. Unlike PEODDN, porocarcinoma typically presents with rapid growth, ulceration, bleeding, and may show infiltrative borders. While PEODDN exhibits cornoid lamellae originating from eccrine ducts with benign cytological features, porocarcinoma demonstrates malignant cytological features including nuclear pleomorphism, atypical mitoses, and invasive growth patterns.¹² Misdiagnosis could lead to inadequate treatment, as porocarcinoma requires more aggressive management including wide local excision and potential adjuvant therapy.¹²

Although the pathogenesis of PEODDN remains unclear, recent genetic studies have provided valuable insights. Somatic mosaicism of the GJB2 gene, which encodes the gap junction protein Connexin26, is hypothesized to play a role in this process.¹³ This finding is particularly interesting given the predominant expression of Connexin26 in the palm, soles, hair follicles, and eccrine sweat glands, which are commonly affected by PEODDN.^13–15 The hypothesis that PEODDN represents a mosaic form of keratitis-ichthyosis-deafness (KID) syndrome, as proposed by Lazic et al, further supports the role of GJB2 mutations.¹³ Both of which share similar histopathological features and involve Connexin26 dysfunction. However, the localized nature of PEODDN contrasts with the generalized involvement in KID syndrome, likely reflecting the timing and extent of somatic mutations during embryonic development.

PEODDN is associated with various cutaneous and systemic conditions; however, the significance of these associations remains unclear. The reported disorders include hearing loss and developmental delay, squamous cell carcinoma, Bowen disease, severe alopecia and onychodysplasia, polyneuropathy and hyperthyroidism, breast hypoplasia, and hemiparesis, seizure and scoliosis.^16–21 Rarely, PEODDN was found to coexist with other skin diseases, ie, linear epidermal nevus, calcinosis cutis, psoriasis, and psoriasiform variant of PEODDN.^22–26

Treatment of PEODDN remains challenging, with variable responses reported in the literature. Most reported therapies are ineffective, such as keratolytic agents, topical calcipotriol, topical retinoids, topical corticosteroids, systemic retinoids, and cryotherapy.^27–29 CO₂ lasers, photodynamic therapy, and a combination of erbium and CO₂ lasers have shown the most promising results.^30,31 Spontaneous resolution has also been reported in some cases.^32,33 In our case, we opted for CO₂ laser treatment because of its reported efficacy and minimal scarring. The successful outcome at one-month follow-up supports the use of this modality for solitary PEODDN lesion, although a long-term follow-up is necessary to assess recurrence.

Conclusion

This case report highlights the atypical presentation of PEODDN, emphasizing the importance of considering this rare entity in the differential diagnosis of solitary keratotic lesion, even at late-onset and unusual locations. Characteristic histopathological findings are crucial for accurate diagnosis. Our case also provides valuable insights into the pathogenesis, associated conditions, and treatment options for PEODDN. Clinicians should be aware of the diverse manifestations of PEODDN and its potential associations with several conditions. For optimal management of complex cases, a multidisciplinary approach involving dermatologists, plastic surgeons, dermatopathologists, and medical or radiation oncologists can be warranted in cases with extensive involvement, systemic associations, or suspicion of malignancy. Long-term follow-up is recommended for all patients with PEODDN to monitor potential complications and assess the treatment efficacy. We also acknowledge that as a single-case report, our experience has inherent limitations; continued documentation of similar cases will be valuable to further characterize this rare disorder. As our understanding of the genetic basis of PEODDN continues to evolve, future research should focus on elucidating the full spectrum of GJB2 mutations and their functional consequences. Additionally, novel treatment approaches such as targeted therapies based on underlying genetic alterations may offer more effective options.