Table 18.1 Nomenclature of bone tumors

• Pseudogout
• Osteomyelitis
WORKUP
Physical examination and laboratory evaluation
LABORATORY TESTS
• Gram stain and culture (aerobic and anaerobic)
1. Aspirated material from:
a. Advancing edge of cellulitis
b. Any vesicles
2. Swab of any drainage material
3. Punch biopsy (in selected patients)
• Blood cultures
• ALOS titer (in suspected streptococcal disease)
Despite the above measures the cause of cellulitis remains unidentified in most patients.

IMAGING STUDIES
CT or MRI in patients with suspected necrotizing fasciitis (deep-seated infection of the subcutaneous tissue that results in the progressive destruction of fascia and fat): patients present with diffuse swelling of an arm or leg followed by the appearance of bullae filled with clear fluid or maroon, violaceous fluid.
TREATMENT
NONPHARMACOLOGIC THERAPY
Immobilization and elevation of the involved limb
ACUTE GENERAL Rx
Erysipelas
• PO: penicillin V 250 to 500 mg qid
• IM: penicillin G (procaine) 600,000 U bid
• IV: penicillin G (aqueous) 4 to 6 million U/day
NOTE: Use erythromycin, cephalosporins, clindamycin, or vancomycin in patients allergic to penicillin.
Staphylococcus cellulitis
• PO: dicloxacillin 250 to 500 mg qid
• IV: nafcillin, 1 to 2 g q4-6h
• Cephalosporins (cephalothin, cephalexin, cephradine) also provide adequate antistaphylococcal coverage except for MRSA.
• Use vancomycin in patients allergic to penicillin or cephalosporins and in patients with methicillin-resistant S. aureus (MRSA)
H. influenzae cellulitis
• PO: amoxicillin, cefaclor, cefixime, or cefuroxime
• IV: cefuroxime or ampicillin; TMP-SMX in patients allergic to penicillin
• Amoxicillin is ineffective in ampicillin-resistant strains (approxi-mately 30%), IV cefuroxime is indicated in severely ill patients.
Vibrio vulnificus
• Doxycycline 100 mg IV or PO bid +/- third-generation cephalosporin
• IV support and admission into ICU (mortality rate >52% in septic shock)
Erysipelothrix
• Penicillin
Aeromonas hydrophila
• Aminoglycosides
• Chloramphenicol
DISPOSITION
Prognosis is good with prompt treatment.

Cellulitis

BASIC INFORMATION
DEFINITION
Cellulitis presents as a hot, sometimes tender area of confluent erythema of the skin due to infection of the deep subcutaneous layer. It often affects the lower leg, causing an upward-spreading, hot erythema, and occasionally will blister, especially if oedema is prominent. It may also be seen affecting one side of the face. Patients are often unwell with a high temperature. It is usually caused by a streptococcus, rarely a staphylococcus, and sometimes community acquired MRSA. In the immunosuppressed or diabetic patient Gram-negative organisms or anaerobes should be suspected.
There may be an obvious portal of entry for infection such as a recent abrasion or a venous leg ulcer. The web spaces of the toes should be examined for evidence of fungal infection. Skin swabs are usually unhelpful. Confirmation of infection is best done serologically by streptococcal titres: antistreptolysin O titre (ASOT) and antiDNAse B titre (ADB).
Erysipelas is the term used for a more superficial infection (often on the face) of the dermis and upper subcutaneous layer that clinically presents with a well-defined edge. However, erysipelas and cellulitis overlap so it is often impossible to make a meaningful distinction.
SYNONYMS
Erysipelas (cellulitis generally secondary to group A ß-hemolytic streptococci)
EPIDEMIOLOGY & DEMOGRAPHICS
Cellulitis occurs most frequently in diabetics, immunocompromised hosts, and patients with venous and lymphatic compromise.
PHYSICAL FINDINGS & CLINICAL PRESENTATION
Variable with the causative organism
• Erysipelas: superficial-spreading, warm, erythematous lesion distinguished by its indurated and elevated margin; lymphatic involvement and vesicle formation are common.
• Staphylococcal cellulitis: area involved is erythematous, hot, and swollen; differentiated from erysipelas by nonelevated, poorly demarcated margin; local tenderness and regional adenopathy are common; up to 85% of cases occur on the legs and feet.
• H. influenzae cellulitis: area involved is a blue-red/purple-red color; occurs mainly in children; generally involves the face in children and the neck or upper chest in adults.
• Vibrio vulnificus: larger hemorrhagic bullae, cellulitis, lymphadenitis, myositis; often found in critically ill patients in septic shock.
ETIOLOGY
• Group A ß-hemolytic streptococci (may follow a streptococcal infection of the upper respiratory tract)
• Staphylococcal cellulitis
• H. influenzae
• Vibrio vulnificus: higher incidence in patients with liver disease (77%) and in immunocompromised hosts (corticosteroid use, diabetes mellitus, leukemia, renal failure)
• Erysipelothrix rhusiopathiae: common in people handling poultry, fish, or meat
• Aeromonas hydrophila: generally occurring in contaminated open wound in fresh water
• Fungi (Cryptococcus neoformans): immunocompromised granulopenic patients
• Gram-negative rods (Serratia, Enterobacter, Proteus, Pseudomonas): immunocompromised or granulopenic patients
DIAGNOSIS
DIFFERENTIAL DIAGNOSIS
• Necrotizing fasciitis
• DVT
• Peripheral vascular insufficiency
• Paget’s disease of the breast
• Thrombophlebitis
• Acute gout
• Psoriasis
• Candida intertrigo