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[8 min read] Managing blistering dermatoses in primary care
Blistering dermatoses in adult patients are a challenge not only for dermatologists but also for primary care physicians. Most of these dermatoses fall into one of four categories: inherited, pemphigus, autoimmune, and other. Here is a guide to managing these presentations in general practice.
Take a good history
The initial approach to a blistering rash is to determine whether a biopsy is needed. Unfortunately, most of the systemic blistering dermatoses in adults (i.e. pemphigus, bullous lupus, etc) often need a pathological diagnosis. However, a careful history can help a primary care doctor differentiate blistering aetiologies that may not need a biopsy for recognition. These include coma blisters, friction blisters, oedema blisters, post-burn or post-graft blisters, and bullous diabeticorum. Oftentimes, avoiding unnecessary biopsy in these patients can be very helpful as these patients are generally at high risk of poor wound healing. In general, recognising that blisters are limited to sites of trauma or pressure in a patient with underlying oedema, anasarca, or immobility can help a doctor determine if a patient truly has a systemic process causing blistering of the skin.
When a diagnosis is unclear, it is safer to take a biopsy, or better yet, refer to a specialist for further evaluation. In general, it is better to take a 4 mm punch biopsy rather than a shave when evaluating a blistering rash of unclear aetiology. Site of the biopsy matters as well. Sampling the edge of a fresh blister is best for histology architecture, and sampling perilesional skin is best for immunofluorescence staining. If you do not readily have access to dermatopathology resources, it’s usually best to refer these patients to a specialist who routinely performs these procedures.
Common blistering dermatoses in general practice
Contact dermatitis can be related to irritants or allergies, with the classic example being poison ivy. Exam findings show a geometric configuration to the rash, and a deeper dive into the patient’s history reveals exposure to some sort of trigger. This could be plant matter, nickel, or antibacterial ointments just to name a few. Biopsy or patch testing may or may not be helpful, The number one treatment includes avoidance and topical steroids. Severe cases may need a short course of systemic steroids.
Dermatitis herpetiformis is classically located on the elbows, buttocks, back, neck, and knees and is incredibly itchy to the patient. As a result, many patients present to the clinic with erosions from scratching and de-roofing the blisters. Biopsy and serologic testing for antigliadin or anti-endomysial antibodies may assist with making the diagnosis. Dermatitis herpetiformis is associated with gluten insensitivity and may be treated with a gluten-free diet and Dapsone. Always remember to check for G6PD deficiency before starting Dapsone therapy.
Shingles is a vesicular rash that can present with blisters. This is associated with the varicella-zoster virus. Healthy patients will present with grouped vesicles on an erythematous base distributed along a unilateral dermatome. It’s important to recognise shingles early. Early recognition and treatment are associated with better outcomes and a lower risk of post-herpetic neuralgia. When in doubt, empiric treatment is favoured if there are no contraindications, and a confirmatory viral swab or biopsy can be taken pending results. The use of topical steroids to aid with healing and inflammation remains controversial at this time.
Patients with bullous arthropod rash have a robust, allergic skin response to bug bites in the form of a blistering rash. This condition is more common in children but may be associated with lymphoma when it occurs in adults. Skin biopsy can be helpful and shows eosinophilic spongiosis. Treatment of bullous arthropod includes topical steroids and avoidance of inciting triggers (i.e. mosquito nets, flea treatments for pets, bug spray, etc.).
Pemphigus, pemphigoid, and other autoimmune bullous dermatoses
Systemic causes of blistering diseases are fairly uncommon but difficult to treat. The pemphigus family of blistering diseases is caused by autoantibodies to desmosomal proteins which disrupt cell-to-cell adhesions in the skin. These dermatoses, which include pemphigus vulgaris and paraneoplastic pemphigus, will result in blisters occurring in the middle of the epidermis. On the other hand, autoimmune subepidermal blistering dermatoses are mediated by autoantibodies that attack the basement membrane zone. These include bullous lupus, bullous pemphigoid, and linear IgA bullous dermatoses. Because the pathology is deeper in the skin, the blister occurs underneath the epidermis. If one of these dermatoses are is suspected, it is best practice to refer the patient for specialist care. Many of these conditions are chronic, relapsing in nature with a need for strong, steroid-sparing systemic immunosuppressants.
Learn more in the Professional Diploma program in General Dermatology.
Ali Alikhan and Thomas L.H. Hocker. Review of Dermatology. 1st edition. Elsevier 2017. Chapter 3: General Dermatology.
Read about diagnosing blistering dermatoses in older adults.
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