TTP and HUS

We were taught that TTP has the possibility of neurological symptoms while HUS is mostly renal, and that HUS is more common in children.

ManUtdForever said:

Any differential diagnosis for these two diseases?

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Anything that can cause a hemolytic anemia, thrombocytopenia, ecchymosis, purpura, acute renal failure, etc. (either occurring in concert or as isolated symptoms) should certainly be included in your differential diagnosis. You can come up with a whole host of events that could easily lead to one or more of the signs/symptoms described above.

As far as TTP and HUS are concerned, the etiologies are distinctly different, although the symptoms sometimes blur the lines between which syndrome the patient actually has (i.e. the presence of neurological symptoms in a child with ARF does not automatically rule out HUS). The rather distinct etiologies are what I personally consider as the main difference between the two. TTP is due to a deficiency in ADAMTS13, a metalloprotease that breaks vWF multimers into smaller fragments. The deficiency in ADAMTS13 (either because of an inherited deficiency or antibodies that neutralize the protein) leads to larger vWF multimers which activate the clotting cascade. It is also associated with a classic pentad of symptoms: fever, CNS deficiencies, acute renal failure, microangiopathic hemolytic anemia and thrombocytopenia. If you see any combination of these five symptoms, your radar should sound for TTP.

HUS is classically seem in children who have previously eaten undercooked meat (this may also be called Typical HUS). It also generally has marked renal failure and with the absence of neurological/CNS symptoms. The rest is pretty similar to TTP. The E. coli in the meat produces Shiga-like toxin, which injures endothelial cells and leads to activation of the clotting cascade, and so on and so forth.

You probably knew all of this, but just for completeness, this is what I consider as the main difference between the two.

ManUtdForever said:

What is the main difference between thrombotic thrombocytopenic purpura and hemolytic uremic syndrome?

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This is what Medscape says about it.

Medscape Article said:

Clinical differentiation of HUS and TTP can be problematic and differentiation is often based on the presence of CNS involvement in TTP and the more severe renal involvement in HUS. In HUS, an antecedent history of diarrheal illness is more often present. In fact, some investigators are suggesting a clinical classification of HUS based on the presence or absence of diarrhea. In children, the distinction between HUS and TTP may be of more importance as general supportive measures, with dialysis as needed, is the standard therapy versus plasma exchange. However, albeit somewhat controversial, plasma exchange is performed in adults with HUS so the differentiation has less therapeutic implications at present.

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ManUtdForever said:

What is the main difference between thrombotic thrombocytopenic purpura and hemolytic uremic syndrome?

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You have a high risk of dying with TTP and a lower risk of dying with HUS.