Acquired periungual fibrokeratoma developing after acute staphylococcal paronychia

ARTICLE

Auteur(s) : Engin Sezer¹, Alina G Bridges², Dogan Koseoglu³, Jale Yuksek¹

¹Department of Dermatology, Gaziosmanpasa University School of Medicine, Tokat, 60100 Turkey
²Department of Dermatology, Mayo Clinic, Rochester, Minnesota, USA
³Department of Pathology, Gaziosmanpasa University School of Medicine, Tokat, Turkey

A 21-year-old male patient presented with a 6-month history of asymptomatic periungual papules involving his left middle finger. According to his medical history the lesions were preceded by an acute, suppurative Staphylococcus aureus paronychia that responded to oral clarithromycin treatment without any surgical intervention. The patient denied any history of previous trauma, was otherwise healthy and took no medication. On examination, two pink, hyperkeratotic periungual papules protruded laterally from the nail fold, resulting in thinning and a groove-like depression of the subjacent nail plate on the left middle finger. Scarring on the inner sides of the lesions was also observed. The lesion on the lateral side showed a pedunculated, finger-like appearance with a verruciform hyperkeratotic surface, while the medial papule was dome-shaped (figure 1A). There were no other cutaneous or mucosal abnormalities. The histopathological examination revealed prominent hyperkeratosis overlying an acanthotic epidermis with hypergranulosis and elongation of the rete ridges. The dermal core was composed of dense interwoven bundles of collagen fibers, often vertically-oriented and admixed with a rich vascular supply (figure 1B). Hair follicles and neural tissue were not detected. The Verhoeff-van Gieson elastin stain revealed decreased elastic fibers in the dermis. A diagnosis of acquired periungual fibrokeratoma (APF) was confirmed by the clinicopathological features. Complete surgical excision under local anesthesia was performed and no recurrence was noted during a 1-year follow-up period.

APF is clinically characterized by either elongated, finger-like protrusions or dome shaped papules with hyperkeratotic tips located on the periungual region of the fingers or toes. The histopathological features consist of a hyperkeratotic and acanthotic epidermis overlying the dermal fibrous proliferation with collagen bundles, often vertically-oriented and admixed with prominent vascularity. The unusual findings of parakeratosis with serum and blood inclusion on the tip of the lesion in our case might be related to recurrent superficial trauma to these sausage-like projections. The aetiology of this entity is unclear. Although localization of the lesions on the acral regions suggests a traumatic origin, history of trauma is identified in only a small subset of patients [1]. A case of APF with granulation tissue accompanying an ingrown nail has also been described in the literature [2]. To our knowledge, this is the first report of APF with development of lesions after an acute S. aureus paronychia. On the other hand, staphylococcal paronychia is usually preceded by a minimal trauma on the periungual region. Thus, the development of APF after a staphylococcal infection is not considered unusual, and we suppose that a careful history of previous paronychial infection should be investigated in patients who present with APF. Kint et al. suggested that APF may be a reactive phenomenon with neoformation of collagen by the fibroblasts [3]. We are in agreement with this opinion and we believe that S. aureus may have triggered a dermal fibroblastic connective tissue reaction in our patient. A recent report indicating an increased migration rate of fibroblasts incubated with S. aureus enterotoxin B also supports this theory [4]. There are also other reports in the literature defining infectious agents as a cause for fibroblastic tissue proliferation. Fibrous, long-spacing collagen, which is a distinct ultrastructural form of collagen present in normal tissue, has been shown to be markedly increased in patients with bacillary angiomatosis [5]. The differential diagnosis of APF includes a Koenen’s tumour of tuberous sclerosis, a supernumerary digit, and periungual verrucae. Although Koenen’s tumour is characterized by pedunculated, flesh-colored periungual papules, lack of other clinical findings of tuberous sclerosis such as seizures, mental retardation, hypopigmented ash leaf-shaped macules, angiofibromas on the face, and Shagreen patches helped us to exclude the diagnosis in this case. Supernumerary digits are present at birth, clinically appear on the base of the fifth digit, and show multiple nerve bundles in the dermis. Lack of epidermal koilocytes and papillomatosis, as well as the presence of the thickened dermal collagen bundles, ruled out a diagnosis of periungual verruca. The formation of scarring on the inner sides of the lesions, despite a history of surgical intervention, suggests that fibrotic proliferation as a tissue response to S. aureus infection might also result in this clinical appearance in association with APF.

Acknowledgements

References

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3 Kint A, Baran R, De Keyser H. Acquired (digital) fibrokeratoma. J Am Acad Dermatol 1985; 12: 816-21.

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5 Borczuk AC, Niedt G, Sablay LB, et al. Fibrous long-spacing collagen in bacillary angiomatosis. Ultrastruct Pathol 1998; 22: 127-33.