Monday, February 25, 2013

All You Need To Know About Scarlet Fever




This disease is the result of infection by streptococci that elaborate one of three pyrogenic (erythrogenic) exotoxins.
Β-hemolytic streptococcus group A

The incubation period ranges from 1–7 days, with an average of 3 days. The onset is acute and is characterized by fever, vomiting, headache, toxicity, pharyngitis, and chills. Abdominal pain may be present; when this is associated with vomiting prior to the appearance of the rash, an abdominal surgical condition may be suggested. Within 12–48 hr the typical rash appears.

Generally, temperature increases abruptly and may peak at 39.6–40º C (103–104º F) on the 2nd day and gradually returns to normal within 5–7 days in the untreated patient; it is usually normal within 12–24 hr after initiation of penicillin therapy. The tonsils are hyperemic and edematous and may be covered with a gray-white exudate.

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Group A streptococcal pharyngitis with inflammation of the tonsils and uvula.

The pharynx is inflamed and covered by a membrane in severe cases. The tongue may be edematous and reddened. During the early days of illness the dorsum of the tongue has a white coat through which the red and edematous papillae project (i.e., white strawberry tongue). After several days the white coat desquamates; the red tongue studded with prominent papillae persists (i.e., red strawberry tongue, raspberry tongue). The palate and uvula may be edematous, reddened, and covered with petechiae.



Note inflammation of the oropharynx with petechiae on the soft palate, small red spots caused by group A streptococcal pharyngitis.

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The exanthem is red, is punctate or finely papular, and blanches on pressure. In some individuals, it may be palpated more readily than it is seen, having the texture of gooseflesh or coarse sandpaper. The rash appears initially in the axillae, groin, and neck but within 24 hr becomes generalized. Punctate lesions generally are not present on the face. The forehead and cheeks appear flushed, and the area around the mouth is pale (i.e., circumoral pallor). The rash is most intense in the axillae and groin and at pressure sites. Petechiae may occur owing to capillary fragility. Areas of hyperpigmentation that do not blanch with pressure may appear in the deep creases, particularly in the antecubital fossae (i.e., pastia lines). In severe disease, small vesicular lesions (miliary sudamina) may appear over the abdomen, hands, and feet.

 

 
Typical rashes in scarlet fever

   
Flushed face, circumoral pallor (Filatov’s sign), Pastia lines in skin folds

  
Miliary sudamina and “sand paper” or goose skin (shagreen) sign

Desquamation begins on the face in fine flakes toward the end of the 1st wk and proceeds over the trunk and finally to the hands and feet. The duration and extent of desquamation vary with the intensity of the rash; it may continue for as long as 6 wk.

Desquamation on the skin (fine flakes)

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Desquamation on the palms and soles (macrolamellar)


Scarlet fever may follow infection of wounds (i.e., surgical scarlet fever), burns, or streptococcal skin infection. Clinical manifestations are similar to those just described, but the tonsils and pharynx generally are not involved. A similar picture may be observed with certain strains of staphylococci that produce an exfoliative toxin.

Scarlet fever must be differentiated from other exanthematous diseases, including measles (characterized by its prodrome of conjunctivitis, photophobia, dry cough, and Koplik spots), rubella (disease is mild, postauricular lymphadenopathy usually is present, and throat culture is negative), and other viral exanthems. Patients with infectious mononucleosis, have pharyngitis, rash, lymphadenopathy, and splenomegaly as well as atypical lymphocytes. The exanthems produced by several enteroviruses can be confused with scarlet fever, but differentiation can be established by the course of the disease, the associated symptoms, and the results of culture. Roseola is characterized by the cessation of fever with the onset of rash and the transient nature of the exanthem. Kawasaki disease, drug eruption, and toxic shock syndrome must also be considered.

Septic or severe scarlet fever associated with bacteremia or toxemia may manifest high fever and may be complicated by arthritis, jaundice, and hydrops of the gallbladder. Scarlet fever may be differentiated from Kawasaki disease by an older age at onset, absence of conjunctival involvement, and recovery of group A streptococci. Streptococcal toxic shock–like syndrome, associated with the pyrogenic toxins, produces toxicity, fever, shock, tissue injury (necrotizing fasciitis, myositis), pneumonia, rash (local or diffuse erythema, maculopapular, petechial, desquamation), and multiorgan dysfunction (kidney, lung, central nervous system). The shock, local tissue injury, older age, and nonscarlatiniform rash differentiate this syndrome from scarlet fever. Arcanobacterium haemolyticum (formerly Corynebacterium haemolyticum) also produces tonsillitis, pharyngitis, and a scarlatiniform rash in adolescents and young adults. Severe sunburn can also be confused with scarlet fever.

DIAGNOSIS. Although 30% of children with sore throat have a positive throat culture for group A streptococci, only 50% of these have a positive antibody response indicative of active infection rather than colonization. Streptococcal pharyngitis is suggested by age greater than 5 yr, high fever, exudates, tender anterior cervical lymphadenopathy, scarlatiniform rash, and a history of exposure. However, only 15% of children with pharyngitis and 25% of those with exudates have streptococcal infection; 50% of those with streptococcal pharyngitis do not have tonsillar exudates. Clinical judgment does not predict which children may have streptococcal infection, which must be diagnosed by throat culture or antigen detection.

Throat culture is the most useful laboratory aid in reaching a diagnosis in patients with acute tonsillitis or pharyngitis. Selective media give a higher yield than sheep blood agar plates. A positive result for a throat culture may indicate streptococcal pharyngitis, but hemolytic streptococci are common inhabitants of the nasopharynx in well children. Isolation of a group A streptococcus from the pharynx of a child with pharyngeal infection does not necessarily indicate that the disease is caused by this organism. When streptococci are isolated from children with moderate or severe exudative pharyngitis who have petechiae on the palate and cervical adenitis, the diagnosis is more secure. Rapid antigen detection tests are not sufficiently sensitive to be used without a back-up culture. Treatment is, however, recommended for all children with pharyngitis and a positive throat culture or rapid antigen test for group A streptococci, even though in some cases the streptococci represent colonization.

The immunologic response of the host after exposure to streptococcal antigen can be assessed by measuring antistreptolysin O (ASO) titers. An increase in ASO titer to greater than 166 Todd units occurs in more than 80% of untreated children with streptococcal pharyngitis within the first 3–6 wk following infection. This response may be modified or abolished by early and effective antibiotic therapy. ASO titers may be very high in patients with rheumatic fever; in contrast, they are weakly positive or not elevated at all in patients with streptococcal pyoderma; responses in patients with glomerulonephritis are variable. Group A b-hemolytic streptococci also may be recovered from the pharynx of asymptomatic individuals who develop an antibody response to this organism, indicating that subclinical infection has occurred.

Individuals with impetigo may react strongly to stimulation by other streptococcal extracellular products. Anti-DNase (deoxyribonuclease) B provides the best serologic test for streptococcal pyoderma; it begins to rise 6–8 wk after infection. Most patients with streptococcal pharyngitis also develop elevated titers to this enzyme. Patients with pyoderma and pharyngitis also may develop antibody responses to hyaluronidase, but antihyaluronidase (AH) titers are elevated with less regularity than are ASO titers.

A 2-min, inexpensive Streptozyme slide test (Wampole Laboratories, CranburyNJ) is designed to detect antibodies against multiple streptococcal extracellular antigens. This test detects more patients with increased antibody titers than any other single test presently available. Nonspecific (false-positive) reactions have been limited in number, and the test is capable of detecting antibody responses within 7–10 days of infection. However, the strength of the Streptozyme reagent varies from lot to lot, and it may not be specific for antibodies to extracellular products of group A streptococci.

The white blood cell count may or may not be elevated. Because leukocytosis may occur in many bacterial and viral diseases, this finding is nonspecific. Similarly, elevations in the erythrocyte sedimentation rate and C-reactive protein do not help to establish a specific diagnosis.

DIFFERENTIAL DIAGNOSIS.

Acute pharyngitis that is indistinguishable clinically from that caused by group A b-hemolytic streptococci may be caused by many viruses, including Epstein-Barr virus (infectious mononucleosis). A viral cause may be suggested by failure to isolate streptococci and can be identified specifically by viral culture and serologic studies. Infectious mononucleosis may be suggested by the clinical manifestations, the presence of atypical lymphocytes in the peripheral blood, and a rise in heterophil and Epstein-Barr viral antibody titers. Acute pharyngitis similar to that caused by b-hemolytic streptococci may occur in patients with diphtheria, tularemia, toxoplasmosis, infection with Mycoplasma or A. haemolyticum, and, rarely, in individuals with tonsillar tuberculosis, salmonellosis, and brucellosis or infections caused by Neisseria gonorrhoeae, Neisseria meningitidis, and Yersinia enterocolitica. These diseases can be differentiated by appropriate cultures and serologic tests.

 Streptococcal pyoderma must be differentiated from staphylococcal skin disease. Often these bacterial species coexist. The lesions produced are clinically indistinguishable; distinction is made only by culture.

Streptococcal septicemia, meningitis, septic arthritis, and pneumonia present signs and symptoms similar to those produced by other bacterial organisms. The offending pathogen can be established only by culture.
Vinsent’s angina need to be differentiated from streptococcal angina in Scarlet fever

COMPLICATIONS. Complications generally reflect extension of streptococcal infection from the nasopharynx. This may result in sinusitis, otitis media, mastoiditis, cervical adenitis, retropharyngeal or parapharyngeal abscess, or bronchopneumonia. Hematogenous dissemination of streptococci may cause meningitis, osteomyelitis, or septic arthritis. Nonsuppurative late complications include rheumatic fever and glomerulonephritis.

PREVENTION. Administration of penicillin will prevent most cases of streptococcal disease if the drug is provided prior to the onset of symptoms. Except for rheumatic fever (see Chapter 175), indications for prophylaxis are not clear. Oral penicillin G or V (400,000 U/dose) is provided four times each day for 10 days. Alternatively, 600,000 U of benzathine penicillin in combination with 600,000 U of aqueous procaine penicillin may be given as a single intramuscular injection. This approach should be used for institutional epidemics. Children exposed to an individual case at school may be observed carefully.

Management of carriers of group A b{beta}-hemolytic streptococci is controversial. It has been suggested that treatment of the carrier precludes the development of type-specific immunity, thereby leaving the individual susceptible to reinfection later in life. It is probably unnecessary to re-treat asymptomatic convalescent patients with persistently positive throat cultures for group A streptococci, since they are generally carriers who do not have persistent or recurrent streptococcal infections. Children thought to have recurrent streptococcal infections may be carriers who have frequent viral respiratory infections masquerading as streptococcal infections. Parental anxiety may be high after several such episodes. Treatment with a non-penicillin antibiotic (e.g., cephalosporin, erythromycin, clindamycin) may be useful in eradicating the carrier state but should be reserved for the rare problem case.

No streptococcal vaccines are available for clinical use.

TREATMENT. The goals of therapy are to decrease symptoms and prevent septic, suppurative, and nonsuppurative complications. Penicillin is the drug of choice for the treatment of streptococcal infections. All strains of group A b{beta}-hemolytic streptococci isolated to date have been sensitive to concentrations of penicillin achievable in vivo.

Blood and tissue levels of penicillin sufficient to kill streptococci should be maintained for at least 10 days. Children with streptococcal pharyngitis should be treated with penicillin (125–250 mg/dose three times a day) for 10 days. Penicillin G or penicillin V may be employed; the latter is preferable because satisfactory blood levels are achieved even when the stomach is not empty. A single intramuscular injection of a long-acting benzathine penicillin G (600,000 U for children <60 lb and 1,200,000 U for children >60 lb) may be more effective for treatment or prevention of relapse and is indicated for all noncompliant patients or those having nausea, vomiting, or diarrhea.

Erythromycin (40 mg/kg/24 hr), clindamycin (30 mg/kg/24 hr), or cefadroxil monohydrate (15 mg/kg/24 hr) may be used for treating streptococcal pharyngitis in patients who are allergic to penicillin. Generally, relapse rates are lower with regimens other than penicillin. Tetracyclines and sulfonamides should not be used for treatment, although sulfonamides may be used for prophylaxis of rheumatic fever.

Treatment failure, defined as persistence of streptococci after a complete course of penicillin, occurs in 5–20% of children and is more common with oral than with intramuscular therapy. It may be due to poor compliance, reinfection, the presence of b{beta}-lactamase–producing oral flora, tolerant streptococci, or presence of a carrier state. Persistent carriage of streptococci predisposes a small number of patients to symptomatic relapse. Repeating the throat culture after a course of penicillin therapy is indicated only in high-risk situations, such as in patients with a history of previous rheumatic fever. If the throat culture is again positive for group A streptococci, some clinicians recommend a second course of treatment. Persistence after a second course of antibiotics probably indicates a carrier state, which has a low risk for the development of rheumatic fever and does not require further therapy.

Patients with severe scarlet fever, streptococcal bacteremia, pneumonia, meningitis, deep soft tissue infections, erysipelas, streptococcal toxic shock syndrome, or complications of streptococcal pharyngitis should be treated parenterally with penicillin, preferably intravenously. The dose and duration of therapy must be tailored to the nature of the disease process, with daily doses as high as 400,000 U/kg/24 hr required in the most severe infections. Severe, necrotizing infections may require the addition of a second antibiotic (e.g., clindamycin) to ensure complete bacterial killing.

PROGNOSIS. The prognosis for adequately treated streptococcal infections is excellent; most suppurative complications are prevented or readily treated. When therapy is provided promptly, nonsuppurative complications are prevented and complete recovery is the rule. In rare instances, particularly in neonates or in children whose response to infection is compromised, fulminant pneumonia, septicemia, and death may occur despite usually adequate therapy.

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