Quiz slides on dermatological infections.pptx
- 2. Scarlet fever/ Scarlatin Introduction • Primarily a disease of children, • Fatal in the pre-antibiotic era • toxin produced by group A β-hemolytic streptococci. Epidemiology and pathogenesis • Majority of cases - between 1 and 10 years of age, since by the age of 10 years, 80% of the population has developed antibodies. • Most cases follow tonsillitis or pharyngitis - in cooler climates, scarlet fever is most common during the late fall, winter and spring. • ‘surgical scarlet fever’- following wounds, burns, and pelvic or puerperal infections • Erythrogenic toxins types A, B and C which are produced by group A streptococci lead to a delayed-type hypersensitivity reaction. • Patients with antibodies against the toxins are spared the rash, but still develop other symptoms of the infection (e.g. sore throat).
- 3. Clinical features • Commonly preceded by the sudden onset of a sore throat, headache, malaise, chills, anorexia, nausea and high fevers. • May experience vomiting, abdominal pain and convulsions. • The rash begins 12-48 hours later and starts as erythema of the neck, chest and axillae. • After 4-6 hours, the remainder of the body is involved. • The rash–tiny papules on an erythematous background–blanches with pressure. • Resembles a ‘sunburn with goose pimples’ and feels like sandpaper. • Pastia's lines (linear petechial streaks) are seen in the axillary, antecubital and inguinal areas. • The cheeks are flushed and circumoral pallor is present. • The throat is red and edematous and develops an exudate after 3-4 days. • There is tender cervical adenopathy and palatal petechiae. • The tongue is initially white with bright red papillae, but later becomes beefy red (‘red strawberry tongue’). • After 7-10 days, desquamation occurs, most severely affecting the hands and feet, and lasts for 2-6 weeks. • Complications of scarlet fever include otitis, mastoiditis, sinusitis, pneumonia, myocarditis, meningitis, arthritis, hepatitis, acute glomerulonephritis, and rheumatic fever.
- 4. Pathology • Engorged capillaries and dilated lymphatic vessels - most prominent around hair follicles. • Edema and perivascular polymorphonuclear infiltrates are common. • There may be small areas of hemorrhage. • Epidermal spongiosis and prominent parakeratosis are appreciated during the desquamative stage. Diagnosis and differential diagnosis • A clinical diagnosis. • There is almost always an elevated leukocyte count with a left shift. • An eosinophilia of 10-20% is seen after 2-3 weeks of convalescence. • Occasionally, a mild hemolytic anemia with reticulocytosis can occur. • Nose and throat cultures will reliably grow group A streptococci. • Detection of antistreptolysin O (ASO), antihyaluronidase, antifibrinolysin and anti-DNase B antibodies are useful in detecting the streptococcal infection. • Early in the disease, a mild albuminuria and hematuria can be seen. Differential diagnosis: Drug rash/ hypersensitivity reaction; measles, rubella, toxic shock syndrome, SSSS, Kawasaki disease and toxin-mediated erythema.
- 5. Treatment • As with other group A streptococcal infections, penicillin is the drug of choice; a 10-14-day course is usually sufficient. • A clinical response can be expected in 24-48 hours. • Antibiotic treatment as long as 10 days after the onset of symptoms will prevent the development of rheumatic fever. • Erythromycin can be used in penicillin-allergic patients.