skin, soft tissue, and bone infections - … · considerations in skin and soft tissue infection...
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SKIN, SOFT TISSUE, AND BONE INFECTIONSClinical Correlation Series
impetigo
Ecthyma
Cellulitis
Panniculitis
Necrotizing fasciitis
Erysipelas
CONSIDERATIONS IN SKIN AND SOFT TISSUE INFECTIONLocalization – layer(s) of tissue involvedLocalized vs. multifocal; disseminated vs.
symmetricalAcute, (bright red, warm, tender) vs. chronic or
subacute (dusky red, indurated older eschar or ulcer along with papules)
Deep involvement, e.g. muscle (pyomyositis, osteomyelitis, panniculitis
Hematogenous vs. exogenousHost factors, exposures
GENERAL RULES IN SKIN INFECTION
Pustules, tender painful papule or nodule with fluctuance –pyogenic esp. StaphSpreading erythema, painful , recent onset – Strep, PasteurellaBites – cat (Pasteurella), dog (Capnocytophaga), human (Eikenella)Linear nodules – Tularemia, Mycobacterium, Sporothrix, NocardiaVesicles – Herpes, RickettsialpoxSystemic toxicity, pain out of proportion to appearance –Necrotizing fasciitisBullae – Vibrio, Capnocytophaga, CampylobacterGangrene – Polymicrobial including Clostridia, enteric GNREschar – Molds, anthrax, tick borne, septicemiaPurpura – Meningococcus, Strep, StaphPetechiae – Rickettsia, CMV,EBV, HIV (acute)
INFECTION
Mastectomy Group A strepFish Tank M. marinumFresh water AeromonasThorn, moss SporothrixNeutropenic, moist area PseudomonasNeutropenic, tender nodules CandidaSplenectomy CapnocytophagaCirrhosis VibrioPalms, soles Syphilis, RickettsiaEschar Molds, anthrax, RickettsiaLymphadenopathy Bartonella, Tularemia
Finding Organism(s)
SKIN INFECTION: GEOGRAPHIC FACTORS
Lyme disease (Erythema chronicum migrans)Blastomycosis (Ulcerated, verrucous, plaques)Yersinia pestis (Southwest US)Coccidioides (Erythema nodosum)Ehrlichia (RMSF-like illness)Vibrio, mycobacteria (Gulf coast)Leishmania (middle east vets)
FEVER AND RASH: LIFE THREATENING ASSOCIATIONS
Petechial lesions - meningococcal, rickettsialsepsis, TTP*
Mucosal involvement – Stevens-Johnson syndromeBullae – Toxic epidermal necrolysis, VibrioPurpura – meningococcus, staph, strep, or
pneumococus (purpura fulminans) Ecthyma gangrenosum – Gram negative sepsisDigital infarcts – Catastrophic APS**, DIC,***
Capnocytophaga, meningococcus
• *thrombotic, thrombocytopenic purpura• **antiphospholipid antibody syndrome• ***disseminated intravascular coagulation
MISCELLANEOUS CLUES TO ETIOLOGY OF SKIN INFECTION
Urticaria – hepatitis B (autoimmune reaction)Slapped cheek, sock and glove purpura –ParvovirusHemorrhagic pustules – NeisseriaNail puncture foot – PseudomonasAmoxicillin – EBVChronic severe atopy, severe burns – HSVIntrathoracic or intraabdominal involvement –Actinomycosis, TBUnderlying osteomyelitis – S. aureus, BartonellaLung and /or CNS involvement – Nocardia, endemic mycoses, mycobacteria
FEVER AND RASH: IMPORTANT CONSIDERATIONS
History must include risk factor assessment –concurrent diseases, medication, travel, occupational/recreational exposure, animalsThorough exam including entire skin area, mucosa, lymph nodesInfectious and non infectious diseases can coexistSkin biopsy for culture and histology rarely contraindicated Acute retroviral syndrome self-inflicted lesions often not considered
INDICATIONS FOR BIOPSY, FURTHER TESTING PRIOR TO RX FOR FEBRILE RASH
Chronic or recurrent natureUlceration, indurationFailure to respond to seemingly appropriate RxWorsening on RxImmunocompromised host, trauma, any factor suggesting non infectious causeConcurrent disease elsewhere, where skin biopsy much less risky than other tissue
SOME USEFUL TESTS FOR FEVER AND RASH EVALUATION
CXR Mycoplasma, vasculitisCryptococcal antigen AIDS, transplant and feverCBC with differential Drug reaction, parasiteHIV Fever, rash, nodesRPR Palm/sole rashANA, ANCA Arthralgia, renal diseaseSerology for RMSF, Ehrlichia Petechiae, headacheSPEP Pyoderma gangrenosumLFT Urticaria, headache,
petechiaBlood culture Petechia, toxicity,
immunocompromised
Test Suspected etiology,clinical setting
Echthyma – S. aureus
STREPTOCOCCAL ECTHYMA
Carbuncle – S. aureus
Erysipelas
Anthrax
Purpura due to Meningococcus
Pyogenic Cellulitis
Linear, Nodular Lesions: SporotrichoidMycobacteriosis
INFECTIONS OF BONE
LOCALIZATION OF ACUTE, HEMATOGENOUS OSTEOMYELITIS
Arterial blood flows to blind loop sinusoids
CLASSIFICATION OF OSTEOMYELITISPathophysiologic
Acute vs. chronicHematogenous vs. contiguous/traumatic
Therapeutically Based MedullarySuperficialCortical LocalizedDiffuse
OSTEOMYELITIS
medullarysuperficial
localized diffuse
SYMPTOMS OF OSTEOMYELITISPain – esp. hematogenous (pediatric, vertebral)
may be exquisite or vaguemay signal complication, e.g. spread to
epidural spaceindistinguishable from sickle cell pain
crisisFever - uncommon
SIGNS OF OSTEOMYELITISErythema, edema, necrosis, bullae, crepitancePurulence, sinus tractNon-healing ulcer: cause or consequenceVisible bone (decubitus ulcer)Non–union of fractureSeparation of components (joint prosthesis)Elevated WBC, platelets, sedimentation rate , normocytic anemia (of chronic disease)Radiologic findings
PATHOPHYSIOLOGY OF OSTEOMYELITIS
Hematogenous – anatomically abnormal bone, prostheses, metaphyses ,vertebral end plate have either increased blood flow a nidus for infectionContiguous – loss of soft tissue barrier, direct traumaMSCRAMM – microbial surface components that recognize adhesive matrix moleculesBacteria adherent to devitalized bone much more resistant to antibiotics
ETIOLOGIES OF OSTEOMYELITISAcute – S. aureus; Salmonella with sickle diseaseContiguous – skin flora; polymicrobial (fecal flora for decubiti, staph strep, anaerobes for diabetes)Immunocompromised – mycobacteria, fungi, pseudomonasProstheses related – Coagulase positive and negative staph, diphtheroidsVertebral – S. aureus, tuberculosis, endocarditispathogens
SEQUESTRUM OF CHRONIC OSTEOMYELITIS
Devitalized bone
MEDULLARRY (HEMATOGENOUS) OSYEOMYELITIS
Resorbed bone adjacent to growth plate
OSTEBLASTIC RESPONSE TO CHRONIC OSTEOMYELITIS
Hyperdense calcification (involucrum)
MR imaging for osteomyelitis
Marrow edema
Loss of bone
VERTEBRAL OSTEOMYELITIS WITH EPIDURAL COMPRESSION
DIABETIC FOOT ULCER -OSTEOMYELITIS
DIAGNOSTIC PITFALLS IN OSTEOMYELITIS
Imaging may lag in acute settingsImaging may distinguish post surgical or traumatic changesCultures may reflect surface contaminantsBiopsy may yield sampling errorNuclear studies may reflect sterile inflammation due to adjacent soft tissueNeuropathy, decubiti may mask painGenerally, MR most sensitive, x-rays lag 2 or more weeks behind, negative nuclear studies helpful
RX OF OSTEOMYELITISHematogenous often cured with antibiotic aloneChronic types esp if cortical or diffuse, prosthesis related, non-union fracture, diabetes related need debridementPolymicrobial consideration for trauma, contiguous etiologyUsually 6 weeks IV Rx, followed by weeks to months oral agent
MUSCLE INFECTIONQuite rare in absence of trauma, ischemiaS. aureus pyomyositis – HIV related in U.S., no obvious risk in tropicsPsoas abscess – relatively common complication of vertebral osteomyelitis (TB, S.aureus)Parasites – trichinosisViral – influenzae B, but not clinically significantClostridia – part of fulminant septic picture in setting of underlying malignancy
PSOAS ABSCESS
Pyomyositis, ring enhancing lesion