Paroxysmal cold hemoglobinuria (PCH) is an acquired hemolytic anemia caused by immunoglobulin G (IgG) antibodies that sensitize red blood cells (RBCs) at cold temperatures by fixing complement to the RBCs causing intravascular hemolysis on rewarming. PCH usually appears in young children as recurrent high fevers, chills, and passage of red-brown urine. The diagnostic test for PCH is the Donath-Landsteiner test, an in vitro assay for biphasic hemolysis. Herein, we present 2 cases of PCH that occurred within 12 months of each other. We quickly diagnosed the second case and treated the patient successfully, in part due to our recognition of its characteristics based on the first case. PCH is a hemolytic anemia for which there is a specific diagnostic test; the timely recognition of this entity by physicians and laboratory staff will allow prompt, supportive therapy and will raise the odds of quick resolution of hemolysis.

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Fibromuscular dysplasia is a non-atherosclerotic, non-inflammatory vascular disease that is most commonly found in the renal arteries of pre-menopausal women. However, this disease entity has rarely been described in the coronary arteries and small cardiac conduction arteries. To our knowledge, there is no recorded case of fibromuscular dysplasia in small cardiac conduction arteries in infants/children. In this report, we present a case of unexplained death of a 14 month old wherein routine histologic examination failed to reveal a cause of death, but subsequent submission of the cardiac conduction system (atrioventricular [AV] and sinoatrial [SA] node regions) demonstrated the presence of isolated AV nodal artery fibromuscular dysplasia, which was considered the cause of death. The case serves to emphasize the potential importance of evaluating the cardiac conduction system in cases where routine gross and microscopic autopsy fails to reveal an adequate explanation for death.

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