Scarlet fever differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]


Scarlet fever must be differentiated from other diseases that cause skin rash, fever, fatigue, abdominal pain and punctate red macules on the hard and soft palate and uvula, including chickenpox, herpes zoster, erythema multiforme, among others.

Differential Diagnosis

Different rash-like conditions can be confused with scarlet fever and are thus included in its differential diagnosis. The various conditions that should be differentiated from scarlet fever include:[1][2][3][4][5][6][7]

Disease Features
  • It commonly presents with pimple-like lesions surrounded by erythematous skin. Lesions are pustules, filled with pus, which then break down over 4-6 days and form a thick crust. It's often associated with insect bites, cuts, and other forms of trauma to the skin.
Insect bites
  • The insect injects formic acid, which can cause an immediate skin reaction often resulting in a rash and swelling in the injured area, often with formation of vesicles.
Kawasaki disease
  • The presentation is similar to smallpox, although it is often a milder form, with fever, headache, myalgia, back pain, swollen lymph nodes, a general feeling of discomfort, and exhaustion. Within 1 to 3 days (sometimes longer) after the appearance of fever, the patient develops a papular rash, often first on the face. The lesions usually develop through several stages before crusting and falling off.
Atypical measles
  • The most commonly caused disease is the Coxsackie A disease, presenting as hand, foot and mouth disease. It may be asymptomatic or cause mild symptoms, or it may produce fever and painful blisters in the mouth (herpangina), on the palms and fingers of the hand, or on the soles of the feet. There can also be blisters in the throat or above the tonsils. Adults can also be affected. The rash, which can appear several days after high temperature and painful sore throat, can be itchy and painful, especially on the hands/fingers and bottom of feet.
Syphilis It commonly presents with gneralized systemic symptoms such as malaise, fatigue, headache and fever. Skin eruptions may be subtle and asymptomatic It is classically described as:
Molluscum contagiosum
  • The lesions are commonly flesh-colored, dome-shaped, and pearly in appearance. They are often 1-5 millimeters in diameter, with a dimpled center. Generally not painful, but they may itch or become irritated. Picking or scratching the lesions may lead to further infection or scarring. In about 10% of the cases, eczema develops around the lesions. They may occasionally be complicated by secondary bacterial infections.
Toxic erythema
  • It is a common rash in infants, with clustered and vesicular appearance.
Rat-bite fever
  • It commonly presents with fever, chills, open sore at the site of the bite and rash, which may show red or purple plaques.
Parvovirus B19
  • The rash of fifth disease is typically described as "slapped cheeks," with erythema across the cheeks and sparing the nasolabial folds, forehead, and mouth.
Scarlet fever
Rocky Mountain spotted fever
Stevens-Johnson syndrome
  • The symptoms may include fever, sore throat and fatigue. Commonly presents ulcers and other lesions in the mucous membranes, almost always in the mouth and lips but also in the genital and anal regions. Those in the mouth are usually extremely painful and reduce the patient's ability to eat or drink. Conjunctivitis of the eyes occurs in about 30% of children. A rash of round lesions about an inch across, may arise on the face, trunk, arms and legs, and soles of the feet, but usually not on the scalp.
Varicella-zoster virus
  • It commonly starts as a painful rash on one side of the face or body. The rash forms blisters that typically scab over in 7-10 days and clears up within 2-4 weeks.
  • It commonly starts with conjunctival and catarrhal symptoms and then characteristic spots appearing in two or three waves, mainly on the body and head, rather than the hands, becoming itchy raw pox (small open sores which heal mostly without scarring). Touching the fluid from a chickenpox blister can also spread the disease.
Rickettsial pox
Disease Epidemiology Predisposing factors Clinical features Lab abnormalities
Signs Symptoms
Toxic shock syndrome Occurs in both adults and children (9:1 female predominance) Occurs in association with vaginitis during menstruation following tampon use (S. aureus); as a complication of soft tissue infections (S. pyogenes or GAS) or in females undergoing medical abortion (C. sordellii). Hypotension, tachycardia, mucous membrane hyperemia (vaginal, oral, conjunctival) Fever, diarrhea, vomiting, diffuse scarlantiform rash Hyponatremia and uremia. Hepatic dysfunction (total bilirubin, serum asparate aminotransferase or serum alanine aminotransferase levels >2 times upper normal limit), leukocytosis with a polymorphonuclear shift to the left. Platelets < 100,000 per mm3 (thrombocytopenia), pyuria of renal origin.


Occurs in children, usually age 1-4 years Interaction of genetic and environmental factors, possibly including an infection in combination with genetic predisposition to an autoimmune mechanism (autoimmune vasculitis) Non-suppurative, painless bilateral conjunctival inflammation (conjunctivitis), strawberry tongue (marked redness with prominent gustative papillae), deep transverse grooves across the nails may develop (Beau’s lines), lymphadenopathy present(acute, non-purulent, cervical), may lead to coronary artery aneurysms. High and persistent fever that is not very responsive to normal treatment with acetaminophen or NSAIDs,  diffuse macular-papular erythematous rash Liver function tests may show evidence of hepatic inflammation and low serum albumin levels, low hemoglobulin and age-adjusted hemoglobulin concentrations, thrombocytosis, anemia. Echocardiographic abnormalities, such as valvulitis (mitral or tricuspid regurgitation) and coronary artery lesions, are significantly more common in Kawasaki disease. [8] Pyuria of uretheral origin.
Scarlet fever Distributed equally among both genders. Most commonly affects children between five and fifteen years of age. Occurs after streptococcal pharyngitis/tonsillitis Pastia's sign (puncta and skin crease accentuation of the erythema), strawberry tongue, cervical lymphadenopathy may be present. Scarlet fever appears similar to Kawasaki's disease in some aspects, but lacks the eye signs or the swollen, red fingers and toes Characteristic sandpaper-like rash which appears days after the illness begins (although the rash can appear before illness or up to 7 days later), rash may first appear on the neck, underarm, and groin Leukocytosis with left shift and possibly eosinophilia a few weeks after convalescence. Anti-deoxyribonuclease B, antistreptolysin-O titers (antibodies to streptococcal extracellular products), antihyaluronidase, and antifibrinolysin may be positive.


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  2. Mehta N, Chen KK, Kroumpouzos G (2016). "Skin disease in pregnancy: The approach of the obstetric medicine physician". Clin Dermatol. 34 (3): 320–6. doi:10.1016/j.clindermatol.2016.02.003. PMID 27265069.
  3. Moore, Zack S; Seward, Jane F; Lane, J Michael (2006). "Smallpox". The Lancet. 367 (9508): 425–435. doi:10.1016/S0140-6736(06)68143-9. ISSN 0140-6736.
  4. Ibrahim F, Khan T, Pujalte GG (2015). "Bacterial Skin Infections". Prim Care. 42 (4): 485–99. doi:10.1016/j.pop.2015.08.001. PMID 26612370.
  5. Ramoni S, Boneschi V, Cusini M (2016). "Syphilis as "the great imitator": a case of impetiginoid syphiloderm". Int J Dermatol. 55 (3): e162–3. doi:10.1111/ijd.13072. PMID 26566601.
  6. Kimura U, Yokoyama K, Hiruma M, Kano R, Takamori K, Suga Y (2015). "Tinea faciei caused by Trichophyton mentagrophytes (molecular type Arthroderma benhamiae ) mimics impetigo : a case report and literature review of cases in Japan". Med Mycol J. 56 (1): E1–5. doi:10.3314/mmj.56.E1. PMID 25855021.
  7. CEDEF (2012). "[Item 87--Mucocutaneous bacterial infections]". Ann Dermatol Venereol. 139 (11 Suppl): A32–9. doi:10.1016/j.annder.2012.01.002. PMID 23176858.
  8. Lin YJ, Cheng MC, Lo MH, Chien SJ (2015). "Early Differentiation of Kawasaki Disease Shock Syndrome and Toxic Shock Syndrome in a Pediatric Intensive Care Unit". Pediatr. Infect. Dis. J. 34 (11): 1163–7. doi:10.1097/INF.0000000000000852. PMID 26222065.

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