Location is a key consideration, as cellulitis in certain locations—including the eye, perineum, and hand—carries an increased risk of morbidity. Orbital cellulitis—which may be characterized by proptosis, ophthalmoplegia, and pain with extraocular movements—most often results from initial sinusitis, and can lead to vision loss, intracranial infection, and significant invasive disease. Prompt antimicrobial therapy and urgent ophthalmologic consultation are essential, as operative drainage may be required.22,23
When the perineum is involved, a careful exam must be performed to determine the limits of the affected area. Although Fournier’s gangrene is uncommon, it is a life-threatening infection. In one small retrospective study, more than half of the patients presented with a perianal abscess.24
Similarly, the hand is vulnerable to significant infection, particularly if it is inoculated with bacteria from human mouth flora (the well-described “fight bite”). In a review of 100 cases of human fight bites, 18 patients ultimately required amputation.25
Early necrotizing fasciitis is often missed. Clinicians generally expect painful lesions to also have erythema, swelling, and increased warmth—the cardinal signs of inflammation. As a result, early necrotizing fasciitis, which initially presents with pain out of proportion to other dermatologic findings, may be overlooked. In fact, pain can precede significant skin findings by 24 to 48 hours; prior to that, only mild erythema or swelling (with minimal pain, in some cases) may be evident.26,27
The general pattern, however, is for a site with exquisite tenderness to evolve into a smooth, swollen area, then to develop dusky plaques and late-stage full thickness necrosis with hemorrhagic bullae.26 At that point, necrosis can render the skin insensate. Case reviews have found necrotizing fasciitis to be protean, with only 3 findings—erythema, edema, and tenderness beyond the expected lesion borders—present in most patients.27 Assiduous attention to skin pain in the presence of any other skin manifestation is the key to early diagnosis and rapid treatment.
Petechiae/purpura may be severe or benign
Petechiae are flat, pinpoint, nonblanching spots caused by intradermal hemorrhage associated with a wide variety of conditions, ranging from benign (local trauma) to severe (eg, disseminated intravascular coagulation [DIC] and sepsis). Similarly, purpura—larger lesions that may be palpable—can accompany less severe diseases, such as Henoch-Schönlein purpura (HSP), or life-threatening conditions like sepsis and DIC (FIGURE 5). Here, as in many other dermatologic conditions, the key differentiating features are location (local vs diffuse), speed of progression, and signs and symptoms of systemic illness.
FIGURE 5
Signs of a life-threatening condition
Hemorrhagic bullae with surrounding erythema on the lateral thigh of a patient with purpura fulminans from bacterial sepsis.
Localized petechiae are common with direct trauma, as well as barotrauma associated with coughing, vomiting, or even asphyxiation. Location is an important clue. Periorbital petechiae and petechiae on the chest above the nipple line suggest that the lesions were caused by the force of the barotrauma, rather than systemic disease.28 A careful history and physical exam are needed to rule out serious underlying conditions, such as pneumonia, dehydration, and abdominal obstruction.
Petechiae out of proportion to the force applied may be an indication of an underlying bleeding diathesis, including thrombocytopenia, coagulation defects, and some fulminant infections. Idiopathic thrombocytopenic purpura (ITP) and HSP may present with more widespread petechiae/purpura, but without fever or systemic symptoms. ITP can develop spontaneously, after a viral infection or after a child’s inoculation with the measles-mumps-rubella vaccine.29 ITP typically presents as easy bruising and petechiae out of proportion to the condition that caused it. These patients, as a rule, will have a healthy appearance.
Treatment (with steroids, IVIG, or anti-D immunoglobulin) is generally not required for children with ITP unless they have bleeding that is mucosal or substantial, as spontaneous remission is expected. Adults, who are more likely to develop chronic ITP, may benefit from treatment.30
HSP occurs most commonly in children, who may have palpable purpura, typically in the lower extremities, as well as arthritis or arthralgia, abdominal pain, and renal involvement that can progress from microscopic hematuria or proteinuria to renal insufficiency.31 Typically, children whose disease is in the acute phase do not appear to be sick, with an important exception: Those who develop hemorrhage and edema in the bowel wall, resulting in intussusception, have significant abdominal pain and are more likely to need surgical reduction.32
Diffuse petechiae in the absence of any trauma, accompanied by significant signs of systemic illness, may be an indication of fulminant infection, including meningococcemia, DIC, and Rocky Mountain spotted fever (RMSF). (Fever and diffuse petechiae can also be seen in viral exanthema, but patients usually look well and the rash often has both blanching and petechial components.33)