Pterygium in a Case of Bullous Pemphigoid – An Uncommon Association

Dear Editor, A 60-year-old male developed generalized pruritic urticarial lesions, followed by tense fluid-filled blisters for 1 year present predominantly on the trunk, abdomen, and upper and lower extremities. He had a history of developing blisters on the dorsum of his fingers. On examination, multiple tense bullae on an erythematous base and urticarial plaques were present on the above sites. Bulla spread sign was positive, while Nikolsky's sign was negative. His ring fingernails were dystrophic, and pterygium was seen in the right ring fingernail Figure 1a-c. Toenails were relatively spared. However, a single flaccid bulla was present over the proximal nail fold of the right great toenail Figure 1d. Oral, ocular, and genital mucosae were spared. There was no history of trauma to nails. There was no history of developing any violaceous itchy lesions on the body.Figure 1: Nail changes in BP: (a) Proximal nail fold of all fingernails shows depigmentation; (b) pterygium in right ring finger (black arrow); (c) left thumbnail shows horizontal and vertical splitting; (d) single flaccid bulla over proximal nail fold of right great toeDermoscopy of the nails using Dinolite premiere AM4113ZT, 50X showed dorsal pterygium in the right ring fingernail and horizontal and vertical splitting of the nail plate of the left thumbnail Figures 2 and 3. No longitudinal ridges or furrows typical for nail lichen planus were present.Figure 2: Dermoscopy showing a wide band of smooth skin spanning from the proximal nail fold to the nail bed suggestive of pterygium (Dinolite premiere AM4113ZT, 50X)Figure 3: Dermoscopy of left thumbnail showing horizontal and vertical splitting (Dinolite premiere AM4113ZT, 50X)Biopsy from the bullae suggested a subepidermal split with dermal inflammatory infiltrate predominant of eosinophils Figure 4. Direct immunofluorescence from the perilesional skin showed linear staining of the basement membrane with IgG and C3, confirming the diagnosis of bullous pemphigoid (BP) Figure 5. The patient had circulating auto-antibodies directed against BP180 (more than 200 U/ml) by enzyme-linked immunosorbent assay. The patient was started on oral nicotinamide 250 mg four times a day, anti-histamines and topical clobetasol propionate 0.05% ointment, and topical sodium fusidate followed by healing of skin lesions. However, there was no improvement in nail lesions.Figure 4: Biopsy from the bullae showing a subepidermal split with dermal inflammatory infiltrate predominant of eosinophils (H and E, 20x)Figure 5: Direct immunofluorescence showing linear staining of the basement membrane with IgG and C3 (10X)Nail involvement in BP is rare. There are a few reports on paronychia, onychomadesis, anonychia, and pterygium occurring in bullous pemphigoid patients. All components of the nail apparatus express BP antigens at the basement membrane zone (BMZ), which are targeted by the immune system.1,2 Also, the site of the split determines the type of nail changes that develop.3 The proximal nail matrix being an immunoprivileged site is less commonly affected.3,4 When BP and other immune blistering diseases affect nails, it is likely related to long-standing inflammation and local trauma.3 Inflammatory processes cause destruction of the BMZ and hemidesmosome, leading to permanent nail loss.1 The extension of bullae into the nail bed leads to onycholysis. Post-bullous erosions lead to pterygium due to inadequate re-epithelialization to prevent adhesion of the base and the roof of the nail pocket.5 There is lack of evidence on the management of nail changes in BP. Nail manifestations may persist for life and usually do not respond to therapy.1 In our case, the patient had uncontrolled diabetes mellitus in spite of being on oral hypoglycemics, due to which oral corticosteroids could not be started. However, he responded well to oral nicotinamide and topical steroids, and hence, a more aggressive approach was not taken. However, a more aggressive approach might be beneficial in such cases. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.