FEVER AND RASH 2

Peripheral Eruptions These rashes are alike in that they are most prominent peripherally or begin in peripheral (acral) areas before spreading centripetally. Early diagnosis and therapy are critical in RMSF because of its grave prognosis if untreated. Lesions evolve from macular to petechial, start on the wrists and ankles, spread centripetally, and appear on the palms and soles only later in the disease. The rash of secondary syphilis, which may be diffuse but is prominent on the palms and soles, should be considered in the differential diagnosis of pityriasis rosea, especially in sexually active patients. Atypical measles is seen in individuals contracting measles who received the killed measles vaccine between 1963 and 1967 in the United States and who were not subsequently protected with the live vaccine. Hand-foot-and-mouth disease is distinguished by tender vesicles distributed peripherally and in the mouth; outbreaks commonly occur within families. The classic target lesions of erythema multiforme appear symmetrically on the elbows, knees, palms, and soles. In relatively severe cases, these lesions may spread diffusely and involve mucosal surfaces. Lesions may develop on the hands and feet in endocarditis.

Confluent Desquamative Erythemas These eruptions consist of diffuse erythema frequently followed by desquamation. The eruptions caused by group A Streptococcus or Staphylococcus aureus are toxin mediated. Certain disease features may provide diagnostic clues. Scarlet fever usually follows pharyngitis; patients have a facial flush, a "strawberry" tongue, and accentuated petechiae in body folds (Pastia's lines). Kawasaki disease presents in the pediatric population as fissuring of the lips, a strawberry tongue, conjunctivitis, adenopathy, and sometimes cardiac abnormalities. Streptococcal toxic shock syndrome manifests with hypotension, multiorgan failure, and often a severe group A streptococcal infection (e.g., necrotizing fasciitis,. Staphylococcal toxic shock syndrome also presents with hypotension and multiorgan failure, but usually only S. aureus colonization¾not a severe S. aureus infection¾is documented. Staphylococcal scalded-skin syndrome is seen primarily in children and in immunocompromised adults. Generalized erythema is often evident during the prodrome of fever and malaise; profound tenderness of the skin is distinctive. In the exfoliative stage, the skin can be induced to form bullae with light lateral pressure (Nikolsky's sign). In a mild form, a scarlatiniform eruption mimics scarlet fever, but the patient does not exhibit a strawberry tongue or circumoral pallor. In contrast to the staphylococcal scalded-skin syndrome, in which the cleavage plane is superficial in the epidermis, toxic epidermal necrolysis involves sloughing of the entire epidermis, resulting in severe disease. Exfoliative erythroderma syndrome is a serious reaction associated with systemic toxicity that is often due to eczema, psoriasis, mycosis fungoides, or a severe drug reaction.

Vesiculobullous Eruptions Varicella is highly contagious, often occurring in winter or spring. At a given time within a given region of the body, varicella lesions are in different stages of development. In immunocompromised hosts, varicella vesicles may lack the characteristic erythematous base or may appear hemorrhagic. Rickettsialpox is often documented in urban settings and is characterized by vesicles. It can be distinguished from varicella by an eschar at the site of the mouse-mite bite and the papule/plaque base of each vesicle. Disseminated Vibrio vulnificus infection or ecthyma gangrenosum due to Pseudomonas aeruginosa should be considered in immunosuppressed individuals with sepsis and hemorrhagic bullae.

Urticarial Eruptions Individuals with classic urticaria ("hives") usually have a hypersensitivity reaction without associated fever. In the presence of fever, urticarial eruptions are usually due to urticarial vasculitis. Unlike individual lesions of classic urticaria, which last up to 48 h, these lesions may last up to 5 days. Etiologies include serum sickness (often induced by drugs such as penicillins, sulfas, salicylates, or barbiturates), connective-tissue disease (e.g., systemic lupus erythematosus or Sjogren's syndrome), and infection (e.g., with hepatitis B virus, coxsackievirus A9, or parasites). Malignancy may be associated with fever and chronic urticaria .

Nodular Eruptions In immunocompromised hosts, nodular lesions often represent disseminated infection. Patients with disseminated candidiasis (often due to Candida tropicalis) may have a triad of fever, myalgias, and eruptive nodules. Disseminated cryptococcosis lesions may resemble molluscum contagiosum. Necrosis of nodules should raise the suspicion of aspergillosis or mucormycosis. Erythema nodosum presents with exquisitely tender nodules on the lower extremities. Sweet's syndrome should be considered in individuals with multiple nodules and plaques, often so edematous that they give the appearance of vesicles or bullae. Sweet's syndrome may affect either healthy individuals or persons with lymphoproliferative disease.

Purpuric Eruptions Acute meningococcemia classically presents in children as a petechial eruption, but initial lesions may appear as blanchable macules or urticaria. RMSF should be considered in the differential diagnosis of acute meningococcemia. Echovirus 9 infection may mimic acute meningococcemia; patients should be treated as if they have bacterial sepsis since prompt differentiation of these conditions may be impossible. Large ecchymotic areas of purpura fulminans reflect severe underlying disseminated intravascular coagulation, which may be due to infectious or noninfectious causes. The lesions of chronic meningococcemia may have a variety of morphologies, including petechial. Purpuric nodules may develop on the legs and resemble erythema nodosum but lack its exquisite tenderness. Lesions of disseminated gonococcemia are distinctive, sparse, countable hemorrhagic pustules, usually located near joints. The lesions of chronic meningococcemia and those of gonococcemia may be indistinguishable in terms of appearance and distribution. Viral hemorrhagic fever should be considered in patients with an appropriate travel history and a petechial rash. Thrombotic thrombocytopenic purpura is a noninfectious cause of fever and petechiae. Cutaneous small-vessel vasculitis (leukocytoclastic vasculitis) typically manifests as palpable purpura and has a wide variety of causes.

Eruptions with Ulcers or Eschars The presence of an ulcer or eschar in the setting of a more widespread eruption can provide an important diagnostic clue. For example, the presence of an eschar may suggest the diagnosis of scrub typhus or rickettsialpox in the appropriate setting. In other illnesses (e.g., anthrax), an ulcer or eschar may be the only skin manifestation.