impetigo
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Introduction
Superficial infection involving the epidermis characterized by crusted erosions or ulcerations.
Etiology
- Staphylococcus aureus
- most commonly phage group 2, type 71
- etiologic agent of Staphylococcal scalded skin syndrome same
- Streptococcus pyogenes
- primary infection of superficial break in skin
- secondary infection of pre-exsiting dermatosis
- predisposing factors
- colonization of skin by S aureus & S pyogenes
- warm ambient temperature
- high humidity
- dermatosis (esp atopic dermatitis)
- precipitating factors
Epidemiology
- primary infections more common in children
- most common bacterial infection in chidren[10]
- secondary infections occur at any age
- common disorder, very contagious[3]
- 25% of patients are nasal carriers of S aureus
- acquired by person to person contact[2]
Pathology
- vesicle formation in subcorneal or granular layer
- acantholysis
- spongiosis
- perivascular infiltrate of neutrophils & lymphocytes in dermis
- gram positive cocci within neutrophils in vesicles
- elaboration of S aureus exotoxin (exfoliatin)[2]
- same toxin causes Staphylococcal scalded skin syndrome
Clinical manifestations
- durations of lesions: days to weeks
- variable pruritus
- non-bullous: small vesicles or pustules rupture resulting in erosions which become crusted
- bullous:
- crusts may be gold (honey-colored) to hemorrhagic
- lesions round or oval, 1-3 cm in size
- scattered, discrete lesions, may be larger confluent lesions
- satellite lesions occur by auto-inoculation
- itchy, raised, weeping patches with scaly borders that develop honey-colored crusts
- distribution:
- face, arms, legs, buttocks
- bullous: trunk, face, hands, intertriginous sites
- regional lymphadenopathy may be present
Laboratory
- Gram stain of lesion
- Gm+ cocci in chains & clusters within neutrophils
- wound culture
- complete blood count (CBC): +/- leukocytosis
- serology: anti-DNAse beta indicates prior group A Streptococcal infection
- biopsy
Complications
- also see ecthyma
- non suppurative complications of group A streptococci
Differential diagnosis
- non-bullous impetigo
- bullous impetigo
- erysipelas (group A streptococcus)
Management
- topical agents
- may be sufficient for limited disease of head & neck
- topical antibiotic after soaking of crusts
- benzoyl peroxide (prevention)
- systemic antibiotics for more extensive disease
- Staphylococcus aureus
- dicloxacillin 250-500 mg PO QID
- cephalexin
- amoxicillin clavulanate (Augmentin)
- 20 mg/kg/day divided TID for 10 days
- macrolides for penicillin-sensitive individuals
- erythromycin
- clarithromycin 250-500 mg PO BID for 10 days
- azithromycin 250 mg QD for 5-7 days
- clindamycin
- methicillin-resistant Staphylococcus aureus (MRSA)
- mupirocin ointment
- minocycline 100 mg PO BID for 10 days
- doxycycline 100 mg PO BID
- Bactrim DS 1-2 tabs QD
- ciprofloxacin 500 mg PO BID
- group A streptococcus (S pyogenes)
- penicillin VK 250 mg PO TID
- benzathine penicillin
- erythromycin 250-500 mg PO QID for 10 days
- cephalexin 250-500 mg QID for 10 days
- Staphylococcus aureus
- prognosis
- prevention
- reoccurence may occur because of failure to erradicate infection or reinfection from family member
- mupirocin to nares of patient & family members for 5 days
- benzoyl peroxide soap
More general terms
Additional terms
References
- ↑ Color Atlas & Synopsis of Clinical Dermatology, Common & Serious Diseases, 3rd ed, Fitzpatrick et al, McGraw Hill, NY, 1997, pg 604-609
- ↑ 2.0 2.1 2.2 2.3 Medical Knowledge Self Assessment Program (MKSAP) 11, 15, 16, 17, 18. American College of Physicians, Philadelphia 1998, 2009, 2012, 2017, 2018.
- ↑ 3.0 3.1 Geriatrics at your Fingertips, 13th edition, 2011 Reuben DB et al (eds) American Geriatric Society
- ↑ 4.0 4.1 Lewis LS, Steele RW (images) Medscape: Impetigo http://emedicine.medscape.com/article/965254-overview
- ↑ 5.0 5.1 DermNet NZ. Impetigo (images) http://www.dermnetnz.org/bacterial/impetigo.html
- ↑ Hartman-Adams H, Banvard C, Juckett G. Impetigo: diagnosis and treatment. Am Fam Physician. 2014 Aug 15;90(4):229-35. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/25250996 Free Article
- ↑ NEJM Knowledge+ Question of the Week. May 21, 2019 https://knowledgeplus.nejm.org/question-of-week/1657/
- ↑ Koning S, van der Sande R, Verhagen AP et al Interventions for impetigo. Cochrane Database Syst Rev. 2012 Jan 18;1:CD003261. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/22258953
- ↑ Hartman-Adams H, Banvard C, Juckett G. Impetigo: diagnosis and treatment. Am Fam Physician. 2014 Aug 15;90(4):229-35. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/25250996 Free Article
- ↑ 10.0 10.1 10.2 Elkston CA, Elkston DM Bacterial Skin Infections: More Than Skin Deep. Medscape. July 19, 2021 https://reference.medscape.com/slideshow/infect-skin-6003449
- ↑ 11.0 11.1 Kosar L, Laubscher T. Management of impetigo and cellulitis: simple considerations for promoting appropriate antibiotic use in skin infections. Can Fam Physician. 2017;63:615-8. PMID: https://www.ncbi.nlm.nih.gov/pubmed/28807958