CASE PRESENTATION
A 50-year-old female presented to the dermatology clinic for her initial visit, with a concern of multiple dark spots on her skin. The patient reported that approximately 1 year prior to presentation, she noticed an erythematous tender patch on her left upper back 2 days following her second dose of the Pfizer-BioNTech COVID-19 mRNA vaccine. Of note, both doses of the vaccine had been administrated in her right arm. Over the next several days, the lesion gradually lost its erythematous hue and became a nontender round hyperpigmented patch. Approximately 1 month later, she noticed similar tender erythematous plaques gradually developing on her trunk and upper extremities. These lesions similarly progressed to non-tender hyperpigmented patches over the next several days. She continued to develop new lesions over the course of 9 months. No bullous lesions were reported.
Her past medical history was notable for breast cancer treated with left mastectomy and chemoradiation 3 years prior to presentation. Additionally, she started taking amlodipine for hypertension 1 week prior to presentation. She denied taking any other medications both at the time of presentation and for the past year, including over the counter medications such as acetaminophen or NSAIDs. She reported a history of pruritus after taking a sulfa antibiotic many years prior to presentation, but she did not remember the name of that medication. She denied any history of vaccine allergies. Her family history was noncontributory.
On examination, multiple round hyperpigmented patches ranging from 2 to 8 cm in size were seen on the left upper back (Figure 1a) , right forearm, right and left anterior chest wall ((Figure 1b) , left abdomen, and left axilla. The remainder of the cutaneous and mucosal exam was unremarkable. A punch biopsy was obtained from the round hyperpigmented patch on the left upper back. Histopathological examination was notable for post-inflammatory pigmentary alteration with rare eosinophils consistent with a resolving FDE (Figures 2a + 2b ). The patient was reassured and advised to weigh the potential benefits and harms prior to receiving any booster doses of the COVID-19 vaccine.
DISCUSSION :
COVID-19 vaccination has been associated with an array of cutaneous adverse effects, ranging from a localized pruritic erythematous eruption to a case of Stevens-Johnson syndrome. FDE following Covid-19 vaccination has only been reported in a handful of cases [9]. The pathogenesis of FDE following Covid-19 vaccination has yet to be determined. One potential mechanism is an immune response to the polyethylene glycol (PEG) excipient of the mRNA vaccine [8]. Similarly, a reaction to ChAdOx1 nCoV-19 virotopes in adenoviral vectored vaccines [4] has been proposed as a possible mechanism. Notably, polysorbate 80, the vaccine excipient, does not seem to be the culprit allergen [4, 7].
FDE following COVID 19 vaccination appears to have a very low incidence rate, and its outcome is generally favorable. However, our case illustrates the potential for prolonged cosmetic sequelae following FDE secondary to the Pfizer-BioNTech Covid-19 vaccination. As such, a clear conversation about the risk of FDE should be included in the informed consent discussion when weighing the risks and benefits of Covid-19 vaccination and booster doses.