History

Fact Explanation
Fever. The exotoxin produced by the causative organism Streptococcus pyogenes is pyrogenic [1].
Sore throat. A significant number of cases of pharyngitis are caused by group A streptococci [2]. This focus of infection could act as the source in the pathogenesis of scarlet fever.
Headache, nausea, vomiting, myalgia, and malaise. The virulence factors secreted by the organism cause an inflammatory response which results in constitutional symptoms such as these [3].
History of rash. Streptococcal exotoxins are highly destructive to skin, muscle, and other soft tissue, and may cause a rash that later desquamates [4].
References
  1. KIM Y. B.. A PURIFIED GROUP A STREPTOCOCCAL PYROGENIC EXOTOXIN: PHYSICOCHEMICAL AND BIOLOGICAL PROPERTIES INCLUDING THE ENHANCEMENT OF SUSCEPTIBILITY TO ENDOTOXIN LETHAL SHOCK. Journal of Experimental Medicine [online] 1970 March, 131(3):611-628 [viewed 26 August 2014] Available from: doi:10.1084/jem.131.3.611
  2. ZWART S.. Penicillin for acute sore throat in children: randomised, double blind trial. BMJ [online] 2003 December, 327(7427):1324-0 [viewed 26 August 2014] Available from: doi:10.1136/bmj.327.7427.1324
  3. SRISKANDAN SHIRANEE, FAULKNER LEE, HOPKINS PHILIP. Streptococcus pyogenes: Insight into the function of the streptococcal superantigens. The International Journal of Biochemistry & Cell Biology [online] 2007 January, 39(1):12-19 [viewed 26 August 2014] Available from: doi:10.1016/j.biocel.2006.08.009
  4. WOOD TF, POTTER MA, JONASSON O. Streptococcal toxic shock-like syndrome. The importance of surgical intervention. Ann Surg [online] 1993 Feb, 217(2):109-114 [viewed 26 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1242748

Examination

Fact Explanation
Febrile patient. The exotoxin produced by the causative organism Streptococcus pyogenes is pyrogenic [1].
Bright red mucous membranes, scattered petechiae and small red papular lesions on the soft palate on examination of the oral mucosa. Streptococcal exotoxins are highly destructive to skin, muscle, and other soft tissue [2].
Strawberry tongue. Due to a white coating on the tongue with hypertrophied projecting papilla, which results from the effects of the exotoxin [3].
Red, edematous, exudative tonsils. Infection with group A streptococci is the most common bacterial cause of acute tonsillitis beyond infancy so this can act as the source of infection [4].
Exanthem consisting of a fine erythematous punctate eruption imparting a sandpaper like texture to the skin, Eventually giving rise to scarlet macules overlying the generalized erythema, followed by skin desquamation. Due to streptococcal exotoxins that are highly destructive to skin [2].
Pastia lines. This deep red, linear exanthem is seen due to capillary rupture as a result of decreased capillary strength [5].
Cervical lymphadenopathy. It can occur as a result of pharyngitis which can be a source of streptococcal infection [6].
References
  1. KIM Y. B.. A PURIFIED GROUP A STREPTOCOCCAL PYROGENIC EXOTOXIN: PHYSICOCHEMICAL AND BIOLOGICAL PROPERTIES INCLUDING THE ENHANCEMENT OF SUSCEPTIBILITY TO ENDOTOXIN LETHAL SHOCK. Journal of Experimental Medicine [online] 1970 March, 131(3):611-628 [viewed 26 August 2014] Available from: doi:10.1084/jem.131.3.611
  2. WOOD TF, POTTER MA, JONASSON O. Streptococcal toxic shock-like syndrome. The importance of surgical intervention. Ann Surg [online] 1993 Feb, 217(2):109-114 [viewed 26 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1242748
  3. CHILLER KATARINA, SELKIN BRYAN A., MURAKAWA GEORGE J.. Skin Microflora and Bacterial Infections of the Skin. J Invest Dermat SP [online] 2001 December, 6(3):170-174 [viewed 26 August 2014] Available from: doi:10.1046/j.0022-202x.2001.00043.x
  4. GIRISCH M., HEININGER U.. Scarlet Fever Associated with Hepatitis - A Report of Two Cases. Infection [online] 2000 August, 28(4):251-253 [viewed 26 August 2014] Available from: doi:10.1007/s150100070048
  5. CLEMETSON C. ALAN B., BLAIR LILIAN, BROWN ALBERT B.. CAPILLARY STRENGTH AND THE MENSTRUAL CYCLE*. [online] 2006 December, 93(7):279-300 [viewed 26 August 2014] Available from: doi:10.1111/j.1749-6632.1962.tb30520.x
  6. BISNO ALAN L.. Acute Pharyngitis. N Engl J Med [online] 2001 January, 344(3):205-211 [viewed 26 August 2014] Available from: doi:10.1056/NEJM200101183440308

Differential Diagnoses

Fact Explanation
Kawasaki disease. It also presents with fever, desquamating rash, strawberry tongue, etc, but bilateral conjunctival injection is a prominent feature [1].
Measles. It also presents with fever and rash ending with desquamation, but Koplik's spots on the buccal mucosa is pathognomonic of measles [2].
Staphylococcal scalded skin syndrome. It also presents with fever and erythematous rash, but soon large, fragile, thin-roofed blisters appear, which rapidly rupture on the slightest pressure (positive Nikolsky sign) [3].
References
  1. DAJANI A. S., TAUBERT K. A., GERBER M. A., SHULMAN S. T., FERRIERI P., FREED M., TAKAHASHI M., BIERMAN F. Z., KARCHMER A. W., WILSON W.. Diagnosis and therapy of Kawasaki disease in children. Circulation [online] 1993 May, 87(5):1776-1780 [viewed 26 August 2014] Available from: doi:10.1161/01.CIR.87.5.1776
  2. PERRY ROBERT T., HALSEY NEAL A.. The Clinical Significance of Measles: A Review. J INFECT DIS [online] 2004 May, 189(s1):S4-S16 [viewed 26 August 2014] Available from: doi:10.1086/377712
  3. LADHANI S, JOANNOU CL, LOCHRIE DP, EVANS RW, POSTON SM. Clinical, Microbial, and Biochemical Aspects of the Exfoliative Toxins Causing Staphylococcal Scalded-Skin Syndrome Clin Microbiol Rev [online] 1999 Apr, 12(2):224-242 [viewed 26 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC88916

Investigations - for Diagnosis

Fact Explanation
Polymorphonuclear leukocytosis on full blood count. Scarlet fever results from a focus of infection from the bacterial species Streptococcus pyogenes [1]. This results in a neutrophil predominent leukocytosis.
Group A streptococci found on throat culture. Because the diagnosis of a streptococcal infection of the upper respiratory tract on clinical grounds is necessarily presumptive, a culture of the throat provides valuable laboratory confirmation or rejection of the clinical impression [2].
Elevated antistreptolysin-O titres. Streptolysin-O, which is elaborated by the haemolytic streptococci is antigenic [3].
References
  1. CHIOU C.-S., LIAO T.-L., WANG T.-H., CHANG H.-L., LIAO J.-C., LI C.-C.. Epidemiology and Molecular Characterization of Streptococcus pyogenes Recovered from Scarlet Fever Patients in Central Taiwan from 1996 to 1999. Journal of Clinical Microbiology [online] December, 42(9):3998-4006 [viewed 26 August 2014] Available from: doi:10.1128/JCM.42.9.3998-4006.2004
  2. WANNAMAKER L. W.. A Method for Culturing Beta Hemolytic Streptococci from the Throat. Circulation [online] 1965 December, 32(6):1054-1058 [viewed 27 August 2014] Available from: doi:10.1161/01.CIR.32.6.1054
  3. SAINT-MARTIN M. Antistreptolysin-O Determinations in Health and in Disease Can Med Assoc J [online] 1957 Apr 15, 76(8):627-633 [viewed 28 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1823729

Investigations - Screening/Staging

Fact Explanation
Urinalysis revealing red blood cell casts. Poststreptococcal glomerulonephritis is a known complication of scarlet fever [1].
Liver function tests revealing abnormally elevated liver enzymes. Hepatitis is a rare complication of scarlet fever [2].
References
  1. RAMMELKAMP CHARLES H., WEAVER ROBERT S.. ACUTE GLOMERULONEPHRITIS. THE SIGNIFICANCE OF THE VARIATIONS IN THE INCIDENCE OF THE DISEASE 12. J. Clin. Invest. [online] 1953 April, 32(4):345-358 [viewed 26 August 2014] Available from: doi:10.1172/JCI102745
  2. GIDARIS D, ZAFEIRIOU D, MAVRIDIS P, GOMBAKIS N. Scarlet Fever and hepatitis: a case report Hippokratia [online] 2008, 12(3):186-187 [viewed 26 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2504399

Management - General Measures

Fact Explanation
Topical emollients. To soothe the skin that desquamates due to the effects of the exotoxins [1].
References
  1. WOOD TF, POTTER MA, JONASSON O. Streptococcal toxic shock-like syndrome. The importance of surgical intervention. Ann Surg [online] 1993 Feb, 217(2):109-114 [viewed 26 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1242748

Management - Specific Treatments

Fact Explanation
Penicillin (oral). 250 mg given 8 hourly for 10 days. It is given intravenously if odynophagia occurs as a result of pharyngitis. Penicillin inhibits bacterial cell wall synthesis [1].
Erythromycin (oral). 60-100 mg/kg/day. Given in case of penicillin allergy. It blocks the entrance to the tunnel in the large ribosomal subunit, through which nascent peptide chains exit the ribosome. This results in arrest of protein synthesis in bacteria [2].
References
  1. TIPPER DJ, STROMINGER JL. Mechanism of action of penicillins: a proposal based on their structural similarity to acyl-D-alanyl-D-alanine. Proc Natl Acad Sci U S A [online] 1965 Oct, 54(4):1133-1141 [viewed 28 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC219812
  2. TENSON TANEL, LOVMAR MARTIN, EHRENBERG MåNS. The Mechanism of Action of Macrolides, Lincosamides and Streptogramin B Reveals the Nascent Peptide Exit Path in the Ribosome. Journal of Molecular Biology [online] 2003 July, 330(5):1005-1014 [viewed 28 August 2014] Available from: doi:10.1016/S0022-2836(03)00662-4