A report describes a case of a 60-year-old Caucasian man who presented with a 40-year history of chronic plaque psoriasis, worsening in severity over the last 5 years and a 3-month history of intensely pruritic bullous eruptions on the back, hips and hands. He had a history of hypertension, type 2 diabetes mellitus, ischemic heart disease with prior double coronary artery bypass grafting and an L4-L5 lumbar spinal fusion. He regularly consumed amlodipine, ramipril, atorvastatin, aspirin and metformin. He denied any personal or family history of bullous or other cutaneous diseases. He received multiple topical and systemic therapies for psoriasis, including betamethasone dipropionate, prednisolone and methotrexate, but were not successful.

Examination revealed multiple large, fixed, well-demarcated erythematous plaques on the back and typical features of nail psoriasis, including onycholysis, pitting and splinter hemorrhages. The patient also showed multiple vesicles along the edges of the psoriatic plaques on his back and hips and vesiculobullous eruptions on his fingers. 

Histopathology of a vesicle demonstrated subepidermal vesicle formation with dermal neutrophils and lower numbers of eosinophils, similar to conditions like linear immunoglobulin A (IgA) bullous dermatosis and dermatitis herpetiformis (DH). It showed no fungal organisms. Direct immunofluorescence of the perilesional skin on the back revealed fine granular IgA deposits in the papillary dermis without evidence of a linear pattern of IgA deposition within the basement membrane zone. These findings indicated DH, which was to be correlated with clinical and laboratory findings.

The patient denied celiac disease (CD) symptoms like altered bowel habits, abdominal pain, bloating and fatigue. CD serology revealed positive anti-gliadin IgA titers, positive anti-gliadin IgG titers and positive anti-tissue transglutaminase IgA titers. His total serum IgA was 2.5 g/L and serum vitamin D was 70 nmol/L. The gastroenterologist confirmed the diagnosis of CD and Barrett′s esophagus with multifocal high-grade dysplasia for him. The patient subsequently received endoscopic mucosal resection of Barretts segment and was continuously monitored via routine endoscopic surveillance.

He displayed a remarkable improvement in the DH lesions following treatment with a gluten-free diet and dapsone at a daily dose of 25 mg. His anti-gliadin IgA and anti-tissue transglutaminase IgA decreased after 10 months of treatment. 

The patient informed flares of DH within a day of gluten exposure. He then received a tapering dose of dapsone which was ceased after 2 years owing to satisfactory management of DH, with complete resolution of the vesicular lesions on the back and hips. Due to difficulty adhering to a gluten-free diet, the patient continues to experience intermittent flares of vesiculobullous eruptions on the hands.

Despite improvement in DH, the patient′s psoriasis remained severe, with a Psoriasis Area and Severity Index (PASI) score of 25.8. He then received secukinumab at a dose of 300 mg every month. Treatment with this agent over the past 8 years significantly improved psoriatic skin lesions, with a PASI score of 1.8, on his last visit.

Source: Lee R, Lobo Y, Spelman L. Development of dermatitis herpetiformis in chronic plaque psoriasis. Case Rep Dermatol 2021;13:141-7.