Red or violet papule or pustule and later a weeping nodule with central umbilication usually on hand, arm, or face; [CCDM, p. 568]
Orf is a viral infection transmitted from infected ungulates (sheep, goats, reindeer, and musk oxen). The clinical findings are limited to one or more papules and sometimes regional lymphadenitis. The lesion is described as, "a red to violet vesiculonodule, maculopapule or pustule, that progresses to a weeping nodule with central umbilication." Papules may reach 3 cm in diameter and last 3 to 6 weeks. Patients may have a maculopapular rash on the trunk. A related condition is milker's nodule caused by a different Parapoxvirus. [CCDM, p. 568-9] Parapoxviruses infect sheep and goats; the corresponding human infection is called orf. They also infect dairy cattle; the corresponding human infection is called milker's nodes. [PPID, p. 1703] The orf lesion progresses from a papule to a nodule to a 1-2 cm blister to a weeping ulcer to a crusted ulcer. Patients may have low-grade fever and lymphadenitis. [Guerrant, p. 966]
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