Erythema nodosum as first clinical sign of acute Borrelia burgdorferi infection.

Lyme borreliosis is a frequently encountered tick-borne infection worldwide, caused by a spirochete from the Borrelia burgdorferi genoscpecies. In most cases, the initial sign of Lyme disease is the pathognomonic symptom - erythema migrans rash appearing at the site of the thick bite. Оther described cutaneous manifestations besides erythema migrans ‒ such as erythema nodosum (an acute nodular septal panniculitis), papular urticaria, granuloma annulare, psoriatic changes, lichen striatus et atrophicans, Henoch-Schönlein purpura, and morphea ‒ could potentially present as an initial/first sign of acute Borrelia burgdorferi infection. Serological testing for Lyme disease is only reliable after the initial stages of the disease. Additional PCR or serological examinations such as ELISA, immunoblot, indirect immunofluorescence examination could be performed. The diverse cutaneous manifestations of Lyme disease can lead to delays or ineffectiveness in treatment, as these symptoms may not be promptly identified as signs of the infection. Therefore, a comprehensive evaluation of the three key aspects - clinical findings, serology, and histology - is essential and should be considered collectively. We present a 78-year-old female with an acute form of Borrelia infection following a thick bite, manifesting as erythema nodosum on the lower extremities. Serology confirmed the presence of Borrelia infection, and the histological findings were indicative of erythema nodosum. The patient initially received anti-inflammatory and antibiotic medications. Reverse development of the nodules was observed after therapy with ceftriaxone, methylprednisolone, esomeprazole, and local dressings with povidone-iodine. For outpatient care, her regimen consisted of systemic reduction of the corticosteroid therapy, esomeprazole, and doxycycline. Due to the potential triggering of erythema nodosum by valsartan, it was recommended switching to an alternative medication. The rarity of erythema nodosum as an initial or first sign of acute Borrelia infection is being discussed.