• Ulcers. The most common causes in the hospital are venous insufficiency, pyoderma gangrenosum, deep fungal infection, and chronic viral infections. Chronic herpes simplex virus frequently is the culprit in bedridden, immunosuppressed patients. "Any buttock ulcer or any decubitis ulcer that I see gets ruled out for concomitant herpes simplex virus because I find it probably more than 50% of the time," she said.
• Pustules. One cause – disseminated candidiasis – can mimic acne in the immunosuppressed patient. The lesions tend to have a pale center that sometimes is pustular. "You can KOH that center to prove that you’ve got candidiasis," she said. If there’s no pustule, diagnosing disseminated candidiasis can be difficult because the collection of organisms is so small that it’s easily missed on serial sectioning by dermatopathology. Ask for serial sectioning and staining to identify the organism.
• Erythema. Dr. Fox said she divides erythemas into macular, subacute, and erosive. Macular erythema can be a toxin-mediated erythema or due to drug eruption, GVHD, viral exanthema, or Kawasaki disease. Eosinophilia is a common finding in toxin-mediated erythema. "I use it to help rule [erythema] in, rather than to help rule it out," she said.
When a subacute or chronic erythroderma is due to drug hypersensitivity reaction, be aware of two long-term sequellae: thyroid disruption and late-onset cardiac involvement presenting as life-threatening heart failure in people you wouldn’t expect to have heart problems. Dr. Fox said she checks thyroid-stimulating hormone levels monthly for 6 months and warns patients to go to the emergency department if they develop heart symptoms and tell the staff there to call the dermatologist.
One of the lesser-known causes of erosive erythroderma is toxic erythema of chemotherapy. It can take a lot of charts and talking with the primary medical team to make sure this is not toxic erythema necrolysislike GVHD, she said.
Dr. Fox reported having no relevant financial disclosures.
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