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Erythromelalgia is not characterized by a loss of epidermal nerve fiber density

Epidermal nerve fiber density was not abnormal in patients with erythromelalgia following skin biopsies, according to study results published in JAMA Dermatology.

Researchers tested the epidermal nerve fiber density of 52 patients between Sept. 1, 2010, and Sept. 22, 2015, at the Mayo Clinic, Rochester, Minnesota. There were 42 women and 10 men with a mean age of 44 years (range, 13-82 years). Biopsies were performed at the distal leg.

Following the biopsy tests, only 10% of the patients (n = 5) had a loss of epidermal nerve fiber density below the fifth percentile compared with 5% of an age- and sex-matched control cohort.

The five study patients had other conditions known to cause a decrease in epidermal nerve fiber density, such as diabetes (n = 2), numbness of the involved extremities from prior conditions (n = 2) or ulcerations of the lower extremities (n = 1).

Only four patients had abnormalities related to inflammatory changes or amyloid deposition. These were all nonspecific changes.

In comparison, most of the patients demonstrated functional small fiber neuropathy abnormalities, such as hypohidrosis or anhidrosis on the thermoregulatory sweat test (n = 29) and hyperalgesia or hypoalgesia on the heat pain test (n = 21). Only one patient had normal results across all tests.

“Skin biopsy results at the distal leg for [epidermal nerve fiber density] are abnormal in less than 10% of cases, whereas functional tests of small fiber neuropathies (ie, sweating, heat pain testing at the distal foot, blood pressure and heart rate) will reveal at least one abnormality in almost all patients,” the researchers wrote. “Our findings indicate that skin biopsies for [epidermal nerve fiber density] evaluation are not useful for the diagnosis of small fiber neuropathy associated with erythromelalgia.” – by Talitha Bennett

Disclosure : Mantyh reports no relevant financial disclosures. Please see the full study for the other researchers’ relevant financial disclosures.