Purpura results from the extravasation of blood from vasculature into the skin or mucous membranes. A careful evaluation of a patient with a purpuric rash will help differentiate a benign illness from a life-threatening disorder (Fig. 90-1). Although laboratory tests are helpful, a thorough history and physical examination can offer the most information to identify the cause. This chapter provides an overview of the main causes of petechiae and purpura in children.

Purpura fulminans (PF) is a hematologic emergency characterized by rapid progression of vascular collapse including disseminated intravascular coagulation (DIC), skin necrosis, and multiorgan dysfunction.¹ Three forms of this disease have been identified based on the inciting mechanism. Acute infectious PF is the most common form of the disease, and is seen most commonly with severe sepsis during the acute phase of the illness. A hereditary or acquired deficiency of a natural anticoagulant, either protein C or S, or antithrombin III, has been associated with neonatal PF. Idiopathic or postinfectious PF is usually preceded by a benign febrile illness and presents with rapidly progressing purpura which mainly involves the skin and no other organ tissues.^2,3

PF secondary to sepsis may be a complication of severe bacterial infection, most often gram-negative sepsis, or other infections. The organism most commonly implicated in pediatric patients is Neisseria meningitidis (>90%), followed by Streptococcus pneumoniae and group A and group B streptococci.^3,4 Most cases of Staphylococcus aureus sepsis are reported as toxic shock syndrome. Outbreaks occur in semi-closed communities, such as child care centers, college dormitories, and military bases. Transmission occurs by direct contact with secretions or fomites carrying the offending organism.

The sepsis process is initiated by a local intradermal release of endotoxin leading to an inflammatory reaction and increased vascular permeability. The same endotoxin, up to 24 hours later, causes widespread necrotizing vasculitis and microvascular thrombosis by disturbing the anticoagulant and procoagulant pathways, and leading to DIC. There is rapidly progressing hemorrhagic infarction of the skin and other tissues, including the lungs, kidneys, central nervous system, and the adrenal glands. This causes multiorgan failure and carries a high mortality rate.²

The sepsis-induced cutaneous lesions are similar regardless of the causative organism. The clinical course of skin necrosis begins with a region of dermal discomfort that develops into well-demarcated macules (petechiae) and evolves rapidly to purple–black necrotic lesions which are painful, dark, and raised (purpura)² (Fig. 90-2). The progression of skin changes is rapid, occurring within minutes to hours. The purpuric rash in severe sepsis may appear as a generalized rash, or more typically develops in the distal extremities and progresses proximally with acral distribution over the hands and feet.^2–4

Postinfectious PF may present a few days to weeks after a febrile infectious illness. It has been associated with Varicella and Streptococcus infections, although other organisms have been implicated. The hallmark lesions tend to occur on the lower body, especially the thighs, lower legs, buttocks, and in males, the scrotum and penis. Lesions of idiopathic PF tend to spare the distal extremities. Multiorgan failure is uncommon, but may occur later in the course of inadequately treated disease.^2,5

DIAGNOSIS

Even though the purpuric rash is the principal feature of purpura fulminans, it is a late sign of the disease. Instead, children may initially portray other signs and symptoms such as fever, malaise, vomiting, poor perfusion, altered mental status, and hypotension. Most, but not all, patients will be ill-appearing.

It is important to remember that patients who present with petechiae limited to the face, neck, and upper trunk above the nipple line may not have an infectious cause, particularly in well-appearing children. If there is a history of violent coughing or vomiting, the rash may likely be due to increased venous pressure rather than an infectious cause.

The hallmark laboratory abnormalities of PF occur early and are due to the associated DIC. Findings include prolonged clotting times (prothrombin and partial thromboplastin), thrombocytopenia, decreased plasma fibrinogen, and increased plasma fibrin-degradation products. These markers of intravascular coagulation distinguish PF from other causes of skin necrosis, but they are not specific to PF and may occur in DIC of any cause.^2,6

A blood culture is invaluable regardless of whether fever is present or antibiotics have yet been given. Cerebrospinal fluid (CSF) and urine cultures should be obtained once the patient is stabilized. Highly sensitive rapid polymerase chain reaction (PCR) tests are available for detection of the most common serotypes of N. meningitidis, which can be performed on blood, urine, and CSF.⁴

Additional studies that may be useful include a blood gas (which may show acidosis), a complete blood count (which may show leukocytosis), and a lactate. It is crucial to remember that obtaining supplementary studies is not the priority.

MANAGEMENT

The majority of affected patients develop septic shock and DIC.² Early recognition of the disease state and timely treatment is crucial and will decrease mortality. Aggressive systemic organ support is paramount for survival of these patients. Aggressive fluid resuscitation with crystalloids is required to restore intravascular volume. Hypotension may arise despite aggressive fluid resuscitation, and inotropic support may be necessary. Administration of antibiotics should also be initiated as soon as the diagnosis is considered. Empiric broad-spectrum coverage should include a third-generation cephalosporin, such as ceftriaxone (100 mg/d to a max of 4 g/d) or cefotaxime (200 mg/kg/d to a max of 12 g/d) since it provides good coverage against N. meningitidis and streptococcus. Vancomycin (10–15 mg/kg/dose to a max of 1 g/dose) should be added if methicillin-resistant S. aureus is suspected. Once a causative organism is identified with antibiotic sensitivities, the coverage can be narrowed. Fresh frozen plasma (FFP) (10–20 mL/kg every 8–12 hours) should be given to replace the consumed plasma proteins. Transfusion of platelets (10–15 mL/kg) or cryoprecipitate (5 mL/kg) may be indicated if significant thrombocytopenia and/or hypofibrinogenemia is present, especially if there is pathological bleeding.⁷ Transfusion of FFP is also indicated for the initial treatment of neonatal and postinfectious PF.²