MEDizzy - A 66-year-old man presents for evaluation of erythematous

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Cardinal Manifestations and Presentation of Diseases 2

A 66-year-old man presents for evaluation of erythematous skin lesions on his lower extremities that have been present for the past 4 days. One week ago, he was seen by his primary care doctor for acute bronchitis and was prescribed cefuroxime 500 mg bid. His upper respiratory symptoms improved, but the rash developed. He is not having fever, chills, joint pains, myalgias, or hematuria. On physical examination, there are numerous nonblanching palpable erythematous lesions measuring 1–5 mm in diameter. What is the most likely diagnosis?

ExplanationPurpura is seen when red blood cells extravasate into the dermis, resulting in the characteristic lack of blanching with pressure. Purpura can be either palpable or nonpalpable, and this distinction helps to identify the underlying etiology. This patient has palpable purpura, which is caused by either a vasculitis or emboli. Leukocytoclastic vasculitis (LCV) is a cutaneous small-vessel vasculitis and one of the most common causes of palpable purpura. There are many etiologies of LCV including drugs, infections, and autoimmune disease. The most likely etiology in this patient would be the recent use of cefuroxime causing immune complex deposition. Henoch-Schönlein purpura also causes LCV with a lower extremity predominance. However, the age of onset is most often in children and adolescents, and there are associated symptoms including fever, arthralgias, abdominal pain, gastrointestinal bleeding, and nephritis. Ecthyma gangrenosum is an embolic phenomenon associated with gram-negative infection. These lesions are edematous and erythematous papules or plaques that can develop central purpura and necrosis. Both capillaritis and drug-induced thrombocytopenia are associated with nonpalpable purpura.