The hemolytic-uremic syndrome in nonrelated adopted siblings

Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is the clinical triad of thrombocytopenia, anemia, and acute kidney injury. Classically associated with enterocolitis from Shiga toxin-producing Escherichia coli, HUS is also associated with Streptococcus pneumoniae infections; genetic dysregulation of the alternative complement pathway or coagulation cascade; and, rarely, a hereditary disorder of cobalamin C metabolism. These share a common final pathway of a prothrombotic and proinflammatory state on the endothelial cell surface, with fibrin and platelet deposition. Much work has been done to distinguish between the different mechanisms of disease, thereby informing the optimal therapeutic interventions for each entity.

Hemolytic-uremic syndrome

HUS is one of the most common causes of acute renal failure in childhood. D+ HUS is the most common form and usually follows an episode of hemorrhagic colitis due to VTEC or S. dysenteriae type 1. The SLT elaborated by these organisms is responsible for the endothelial damage that is the initial insult in the pathogenesis of the acute renal failure. Excellent supportive care is necessary to reduce the mortality and morbidity due to HUS.

Infection by verocytotoxin-producing Escherichia coli

Verocytotoxin (VT)-producing Escherichia coli (VTEC) are a newly recognized group of enteric pathogens which are increasingly being recognized as common causes of diarrhea in some geographic settings. Outbreak studies indicate that most patients with VTEC infection develop mild uncomplicated diarrhea. However, a significant risk of two serious and potentially life-threatening complications, hemorrhagic colitis and the hemolytic uremic syndrome, makes VTEC infection a public health problem of serious concern. The main reservoirs of VTEC appear to be the intestinal tracts of animals, and foods of animal (especially bovine) origin are probably the principal sources for human infection. The term VT refers to a family of subunit exotoxins with high biological activity. Individual VTEC strains elaborate one or both of at least two serologically distinct, bacteriophage-mediated VTs (VT1 and VT2) which are closely related to Shiga toxin and are thus also referred to as Shiga-like toxins. The holotoxins bind to cells, via their B subunits, to a specific receptor which is probably the glycolipid, globotriosyl ceramide (Gb3). Binding is followed by internalization of the A subunit, which, after it is proteolytically nicked and reduced to the A1 fragment, inhibits protein synthesis in mammalian cells by inactivating 60S ribosomal subunits through selective structural modification of 28S ribosomal ribonucleic acid. The mechanism of VTEC diarrhea is still controversial, and the relative roles of locally acting VT and "attaching and effacing adherence" of VTEC to the mucosa have yet to be resolved. There is increasing evidence that hemolytic uremic syndrome and possibly hemorrhagic colitis result from the systemic action of VT on vascular endothelial cells. The role of antitoxic immunity in preventing the systemic complications of VTEC infection is being explored. Antibiotics appear to be contraindicated in the treatment of VTEC infection. The most common VTEC serotype associated with human disease is O157:H7, but over 50 different VT-positive O:H serotypes have now been identified. The best strategies for diagnosing human VTEC infection include testing for the presence of free VT in fecal filtrates and examining fecal cultures for VTEC by means of deoxyribonucleic acid probes that specify genes encoding VT1 and VT2. Both methods are currently confined to specialized laboratories and await commercial development for wider use. In the meantime, most laboratories should continue to screen for the most common human VTEC serotype, O157:H7, using a sorbitol-containing MacConkey medium.

Cytotoxin-producing Escherichia coli and the hemolytic uremic syndrome

Recently, a new class of diarrhea-associated Escherichia coli has been linked to the hemolytic uremic syndrome. The organisms included in this group produce cell-damaging toxins (cytotoxins) related to Shigatoxin made by S. dysenteriae 1. The most common pathogen in this group is E. coli O157:H7.

Hemolytic uremic syndrome in families

The occurrence of the hemolytic uremic syndrome in three siblings prompted us to study this illness in families. Two groups of patients could be identified when 83 siblings with the syndrome in 41 families were examined. Siblings whose onset occurred within a short time of each other had a relatively good prognosis (19 per cent mortality); those whose onset was more than a year apart had a poorer prognosis (68 per cent mortality). We speculate that an environmental agent may have caused the syndrome in the first group, and that genetic factors may have been important in the second.

Thrombotic thrombocytopenic purpura in four siblings

A family is described in which four members of a sibship of seven suffered from a hematologic and systemic disorder whcih has been fatal in three and has been proved at autopsy to have been fatal in three and has been proved at autopsy to have been thrombotic purpura. The fourth member has probably suffered the same disorder. The clinical laboratory and genetic features of the family are discussed at length. No cause of the disorder has been determined.

Acute renal failure in children: principles of management

Acute renal failure is a complicated disturb ance, which taxes the clinical skills of the physi cian. This paper reviews the metabolic derange ments, the principles of treatment, the conse quences, and the advances recently made in our understanding of the pathophysiology and man agement of acute renal failure.