Purpura, Petechiae, Meningococcemia, HSP, Osler-Webber-Rendu

Vascular disorders may be responsible for petechiae or purpura in children who have normal or increased platelet counts. Meningococcemia and other bacterial infections are critical causes of vascular purpura because of the high associated morbidity and mortality and the critical need to consider the diagnosis and begin therapy rapidly. The purpura is due to either direct vascular invasion by the organism or to an endotoxin-induced Schwartzman reaction. Clinically, erythematous papules are seen initially, but they soon evolve into widespread petechiae with purple to slate-gray purpura.

Disseminated intravascular coagulation (DIC) develops less frequently, causing petechiae and purpura due to both thrombocytopenia and acrocyanosis that progresses to symmetric peripheral gangrene following fibrin deposition. Patients who have DIC are very ill-appearing and in septic shock. Laboratory studies reveal thrombocytopenia, hypofibrinogenemia, and prolongation of the partial thromboplastin time and the prothrombin time.

Other infectious etiologies of vascular purpura include gram-negative sepsis (particularly in association with granulocytopenia or immune suppression), scarlet fever, Haemophilus influenzae infection, Streptococcus pneumoniae infection, Rocky Mountain spotted fever, and disseminated fungal infections.

Viral infections are the most common causes of vascular purpura. Although the purpura occasionally can be due to specific viruses, such as parvovirus B19 or Hanta virus causing hemorrhagic fever, most often it occurs in otherwise well children who have a variety of more routine viral illnesses. The critical clinical issue is to exclude the more serious bacterial infections from the differential diagnosis before assuming a viral etiology. Purpura can be seen in a variety of other illnesses, including glucocorticoid excess, Ehlers-Danlos syndrome, and serum sickness.

Henoch-Schönlein purpura is the most common cause of noninfectious vascular purpura in children. The palpable purpuric lesions are distributed classically on the lower extremities, avoiding the trunk and head. Collagen-vascular disorders also may present with a purpuric rash. The classic "blueberry muffin" baby has a vasculitis that most often is due to congenital toxoplasmosis, rubella, or cytomegalovirus.

Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome) is an autosomal dominant disorder that usually presents with recurrent epistaxis that worsens with age. The most severely affected patients develop epistaxis during childhood, with cutaneous changes beginning to appear at puberty. 

The lesions of vascular purpura are usually palpable. In contrast, the petechiae and purpura of platelet dysfunction typically are nonpalpable. Platelet dysfunctions must be considered in patients who have purpura and normal platelet counts. Clinically significant platelet dysfunctions in children usually are due to a variety of congenital disorders. The clinical history and physical examination generally will allow differentiation of platelet dysfunction and vascular purpura, with the latter usually associated with a more specific rash. Platelet function studies occasionally may be necessary to document a platelet disorder.

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