Soft tissue infections are commonly encountered when caring for children. From finger infections (Whitlow, Flexor Tenosynovitis) to faces (Periorbital cellulitis, Orbital cellulitis) and within pits and creases (Intertrigo, Perianal Strep), anywhere there is skin we may find an infection. Certainly, we are adept at assessment of cellulitis and abscesses, but we often have an uneasy feeling in our stomach as we ponder a deeper problem. Let’s take a minute to digest a Morsel to help us keep the challenging entity of Necrotizing Fasciitis and other Necrotizing Soft Tissue Infections (NSTI) on our Ddx:

Necrotizing Fasciitis: Basics

Rare, but deadly!

• Incidence is lower in children than adults. [PMID 22158285: Jamal 2011]
  • Estimated incidence at 0.08 per 100,000 children. [PMID 22158285: Jamal 2011]
  • Incidence noted to be higher in children < 5 years of age.

• Diagnosis is often delayed. [PMID 27663964: VanderMeulen, 2017]
  • The superficial layers may not clearly depict the underlying severity.
  • May not appear “toxic.”
  • Delays in diagnosis lead to delayed treatment and increased mortality. [PMID 22315006: Endorf, 2012]

• Progresses Rapidly [PMID 27663964: VanderMeulen, 2017]
  • May become critically ill within first 24-48 hours.
  • Can progress as fast as 1 inch / hour [PMID 22158285: Jamal 2011]

• Mortality rates in children range from 5% – 9.4% and as high 59% in neonates. [PMID 27663964: VanderMeulen, 2017; PMID 22315006: Endorf, 2012]

Preferred terminology = Necrotizing Soft Tissue Infections (NSTI)

• Includes several conditions with less specific names like: [PMID 22315006: Endorf, 2012]
  • Necrotizing cellulitis, Necrotizing erysipelas
  • Synergistic necrotizing cellulitis, Hemolytic streptococcal gangrene
  • Bacterial synergistic gangrene, Gangrenous erysipelas

• Of these entities the most commonly encountered clinically are: [PMID 22315006: Endorf, 2012]
  • Necrotizing fasciitis
  • Fournier gangrene

Classically, NSTI is classified as one of 2 groups:

• Type 1: [PMID 22158285: Jamal 2011]
  • Polymicrobial infections
    • Gram-positive cocci, gram-negative rods, and anaerobes
    • Strep, Staph, bacteroides, E. coli, Klebsiella pneumonia, Pseudomonas, and Proteus mirabilis
  • Most common NSTI type in adults.
  • Polymicrobial NSTI I seen more often in infants < 1 year of age.
  • Often related to underlying medical conditions, surgery, or recent trauma.

• Type 2: [PMID 22158285: Jamal 2011]
  • Single pathogen infection
    • Most classically – Group A Strep (GAS)
    • May be also associated with Staph aureus.
    • Community-Acquired MRSA can also be a culprit.
  • Less common for adults.
  • Tend to be seen in previously healthy, immunocompetent, younger patients.
  • Increasing rates over past several decades.
  • Significant increased risk after Varicella infection.

Necrotizing Fasciitis / NSTI Presentation

No exam feature is pathognomonic.

• Most common findings are: [PMID 22158285: Jamal 2011]
  • Localized pain
  • Rash

• The overlying tissues may not be dramatically affected.
  • The infection is present in the deeper layers so the dermis may not be involved until late in the course. [PMID 27663964: VanderMeulen, 2017; PMID 22158285: Jamal 2011]
  • Vesicles, bullae, ecchymosis, subQ emphysema are all late findings.
  • The involved area is often much larger than the overlying skin would indicate. [PMID 22158285: Jamal 2011]

• The “pain out of proportion” that is often mentioned, can be difficult to discern in children (similar to how compartment syndrome is difficult to detect in pediatric patients).

• Certainly, the child with tachycardia and tachypnea in the setting of a possible skin infection should raise concern for NSTI. [PMID 28877051: Sullivan, 2018]

• Patients may develop altered mental status and overt SHOCK.

• There is no known clinical characteristic that is sensitive enough that its absence can exclude the diagnosis. [PMID 27663964: VanderMeulen, 2017]

Risk Factors may be present.

• NSTI can occur without clear risk factors. [PMID 27663964: VanderMeulen, 2017]

• Common risk factors for NSTI in children: [PMID 27663964: VanderMeulen, 2017]
  • Recent Trauma
  • Recent Varicella infection
  • Systemic Illness (ex, Lupus, Sensory Neuropathies)
  • Recent Non-varicella infection (ex, Sinusitis, Pneumonia)
  • Hospitalization

Labs may help, but are also not reliable.

• There is no known lab finding that is sensitive enough that its absence can exclude the diagnosis. [PMID 27663964: VanderMeulen, 2017; PMID 22158285: Jamal 2011]

• The Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) is a scoring system used for adults, but not validated in children. [PMID 27233372: Putnam, 2016]
  • The Pediatric-LRINEC score has been proposed.
  • It only uses CRP and Serum Sodium.
  • CRP > 20 had sensitivity of 95% and Sodium < 135 had a specificity of 95%.

Necrotizing Fasciitis / NSTI Management

Broad-spectrum antibiotics!

• There are not validated algorithms or management plans, but given the aggressive nature of the infection and the potential for it being polymicrobial, giving broad-spectrum antibiotics that also have anti-toxin effects is critical.

• Reasonable option is Clindamycin PLUS Piperacillin-tazobactam PLUS Vancomycin

Get a Surgeon with a Scalpel

• Ultimately, the infection and devitalized tissues need to be excised.
• Consultation with your friendly pediatric surgeon early in the process is also critical.

Moral of the Morsel

• Nec Fasc is NaSTI! Literally and figuratively.
• The issue is more than Skin Deep! The clinical exam may deceive you.
• Be vigilant. Consider risk factors and keep NSTI on your Ddx for localized pain and rash.
• Kill them all and get a knife! Give broad spectrum antibiotics and call your surgeons.

References