Scabies is an ectoparasite caused by the mite Sarcoptes scabiei var hominis, an obligate human parasite. There are about 300 million cases of scabies in the world each year. Common predisposing factors are overcrowding, immigration, poor hygiene, poor nutritional status, homelessness, dementia, and sexual contact. Direct skin-to-skin contact between 15 and 20 minutes is needed to transfer the mites from one person to another. The diagnosis suspected with a clinical history of itch, worse at night, affecting other family members, clinical distribution, and appearance. Definite diagnosis relies on microscopic identification of the mites, eggs, or fecal pellets with 10% potassium hydroxide, ink enhancement, tetracycline fluorescence tests, or mineral oil; other methods include: epiluminescence light microscopy and S. scabiei DNA. The most commonly used treatment modalities are permethrin and ivermectin. Persistence of symptoms for 2-6 weeks after successful treatment is common. Most recurrences are because of reinfection from untreated contacts.

Dermal vascular skin necrosis is associated with a complex group of clinical disorders. Many of these disorders are associated with an underlying abnormality of the PC anticoagulant system or DIC, or both. The clinical appearance and histopathologic features of dermal vascular skin necrosis are similar regardless of the etiology. Acute infectious purpura fulminans is distinct in that an acute vasculitis may be present in addition to microvascular thrombosis. Skin biopsy is a valuable diagnostic tool in the early recognition of these clinical disorders, since skin involvement is frequently an early manifestation of the disease process. Prompt recognition and institution of appropriate therapy at the reversible stages of dermal vascular thrombosis will, it is hoped, reduce the morbidity and mortality currently associated with skin necrosis and purpura fulminans.

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