Hand and Foot Blisters – Can You Recognize the Usual from the Unusual?
The presence of blisters on the dorsum of the hands and feet is a familiar sight with multiple causes. The most common autoimmune cause is bullous pemphigoid, a blistering disease the occurs in older adults over 60 years of age. It often starts with fixed dermal erythema on the trunk or extremities followed by intact tense blisters. This condition is commonly itchy, and biopsies will demonstrate a subepidermal split of the basement membrane with an eosinophilic predominant infiltrate. Biopsy for direct immunofluorescence in addition to regular biopsy is helpful with diagnostic IgG antibodies at the dermal epidermal junction. Other common causes of blisters on the hands and feet are insect bites, infections, drug reactions, burn injuries, trauma (especially friction), and acute allergic contact dermatitis.
In this issue of Advances, two articles describe unusual blistering hand and foot ulcer lesions. Dermatology resident Dr Isumar and colleagues with senior author Dr Afsaneh Alavi, describe 23 patients with pseudoporphyria who were treated at the Mayo Clinic over several years. These patients had photosensitivity with fragile blisters often predominantly on the dorsum of the hands. The lesions differed from porphyria cutanea tarda (PCT) because the patients did not have elevated porphyrin concentrations in the red blood cells, serum, urine, or feces. Just over half of the documented pseudoporphyria patients consumed alcohol (54%), which is the most common association with PCT, and the patients did not have the elevated liver function tests and high iron levels that often necessitate PCT patient phlebotomies. Treatment for pseudoporphyria involves discontinuation of the causative drug, with the most common culprits being nonsteroidal anti-inflammatory drugs, hydrochlorothiazide, and oral retinoids. The most common site for pseudoporphyria blisters is the hands (65%), followed by the feet (17%), and both feet and hands (13%).
Laura Swoboda and colleagues explored blistering disorders of the foot with three case examples. The first patient had an adenocarcinoma of the gastric esophageal junction with treatment using pembrolizumab. The authors ruled out infection (including bullous impetigo) or deeper cellulitis. Biopsy results demonstrated an eosinophilic infiltration consistent with a drug reaction. Pembrolizumab is a chemotherapeutic agent with the potential to cause a blistering drug reaction of the hands and feet. Other common drug associations include sulphonamides and tetracyclines, and, less commonly, terbinafine and nonsteroidal anti-inflammatory drugs. Other prescription drugs associated with the onset of bullous pemphigoid include etanercept, sulfasalazine, furosemide, and penicillin. A direct drug reaction needs to be separated from drugs facilitating other disease processes.
The second case example is a patient with a bullous tinea pedis infection. These infections are associated with a host inflammatory response; the scale extends to the sides of the foot, often with a slight hint of a red active border toward the dorsal aspect of the foot. This feature distinguishes the fungal infection from dry skin associated with the autonomic aspect of neuropathic feet. Tinea often involves the toe webs. Check the fourth and fifth web spaces first because these are the tightest and often the initial web space involved with scale and maceration that will facilitate secondary bacterial colonization. Proximal bacterial infection of the lower leg may be spread by lymphatic connections to the toe web bacteria. The nails may also be involved with a distal subungual or whole nail plate infection. There are more than 20 conditions that can cause toenail abnormalities. Do not assume that nail abnormalities are fungus: clip the involved nail keratin and examine it under the microscope for fungal elements or send scrapings for fungal culture.
The third case is a person with diabetes with noninflammatory blisters on the foot. These blisters are more common with advanced renal disease and leg swelling. They may also be located on the lower leg with trauma that may not be evident to the patient, especially with neuropathic loss of protective sensation. This fragility and the noninflammatory blisters on histologic exam of skin biopsies may be present in patients without a prior documented diagnosis of diabetes. Consider ordering a glycated hemoglobin test on persons over 40 years with undiagnosed lesions on the lower leg or foot. If the value is 6.5 or higher, a diagnosis of diabetes is most likely but requires a second test for verification. Values between 6.0 and 6.4 are consistent with a diagnosis of prediabetes.
Through careful observation and thoughtful consideration, we may unravel the common and rare clinical presentation mysteries. Are you up to the challenge of identifying the correct cause and treatment?
[Tratto da: www.journals.lww.com ]
