|
TTP occurs predominantly in healthy individuals
(acute idiopathic form), although in many cases it can
be associated with some physiological and pathological
conditions (Table
2).
Actually the diagnosis of TTP is based upon the following
clinical symptoms:
| Bleeding manifestations
(petechiae,
ecchymosis, purpura, epistaxis) |
| Thrombotic manifestations |
| |
Neurological
symptoms (coma, convulsions, motor deficits,
headache, visual disorders, altered mental states) |
| |
Renal
symptoms (oliguria, anuria, acute renal insufficiency) |
| Other
symptoms (fever, diarrhoea, vomiting, abdominal
pain) |
| |
|
| The clinical diagnosis
has to be confirmed by the following laboratory data: |
| Thrombocytopenia: |
| |
platelet count <50X109/L |
| Hemolytic anemia: |
| |
hematocrit usually <20% |
| |
Hb <10g/dl |
| |
increased unconjugated
bilirubin |
| |
presence of schistocytes
on peripheral blood smear |
| |
reticulocytosis |
| |
low or unmeasurable haptoglobin
level |
| |
high serum lactate dehydrogenase |
| |
negative Coombs tests |
The value of ADAMTS13 measurements
to establish the diagnosis of TTP is limited. Although
a severe deficiency of ADAMTS13 activity (< 5%) may
be a frequent abnormality in TTP, patients can present
the characteristic features and clinical course of TTP
without severe ADAMTS13 deficiency or even with normal
ADAMTS13 activity (>50%) (31-35).
On the other hand patients can also have severe ADAMTS13
deficiency for many years and yet remain without symptoms
(36,37).
TTP is a differential diagnosis
of other syndromes characterized by the presence
of thrombocytopenia and microangiopathic hemolytic anemia
such as HUS, disseminated
intravascular coagulation (DIC),
the "catastrophic" anti-phospholypid syndrome
(APS), eclampsia,
pre-eclampsia, HELLP syndrome and heparin induced
thrombocytopenia (HIT) (38,39).
The main clinical and laboratory features useful to distinguish
TTP from other thrombotic microangiopathies are summarized
in Table
3
|
