Catastrophic antiphospholipid syndrome in a child with trisomy 21. An acquired thrombopathy with a discussion of thrombopathies in childhood.

Antiphospholipid syndrome (APLS), an acquired thrombophilic disorder involving autoantibodies against phospholipids and phospholipid-binding proteins, is often accompanied by autoimmune disease but also occurs in the absence of any documented autoimmune disease. It is known to be more common in individuals with trisomy 21. Catastrophic APLS (CAPLS), a rare accelerated form of APLS, leads to acute multisystem organ failure, with microthrombi in multiple organs and a mortality rate of 50% or greater. The youngest case of APLS was reported in a 7-year-old child. We report the pathologic findings in a case of CAPLS in a 2-year-old girl with trisomy 21 who presented with an insidious skin rash, which was rapidly followed by multiorgan failure and death. All major criteria for the diagnosis of CAPLS were met, including the involvement of 3 or more organ systems, precipitous clinical deterioration, positive serology for APL, and noninflammatory microthrombi in at least one organ which, in this case, included multiple sites: skin, lungs, intestinal tract with necrotizing enterocolitis, and spleen, with multiple infarcts all documented at autopsy.