What
is Atypical Hemolytic Uremic Syndrome?
Atypical Hemolytic-uremic syndrome (HUS) is a
syndrome characterized by three major problems areas: 1) progressive renal failure 2) problems associated
with red blood cell and platelet counts and 3) problems that occur in the
vascular system.
Atypical HUS should be differentiated from “regular or
typical” HUS because the diseases have quite a few differences. Regular HUS is typically caused by the E-Coli
virus, and while it is quite a severe disease, if the patient can recover from
the disease, they may live the rest of their lives without another
episode. Atypical HUS patients, however,
frequently have recurring bouts with the disease.
The
Details
While kidney failure may be the most obvious
characteristic of this disease, the disease does not originate in the
kidney. Instead, the root of the problem
originates in either the blood or the vascular system. Microangiopathic hemolytic anemia
occurs. This long word simply means that red blood cells are shattered and
destroyed, because the small blood vessels are obstructed. Obstructed by what? Good question. The blood vessels are obstructed by very
small clots. Clots, as you know, are
usually good things. Clots occur when
platelets rush to a site to stop bleeding.
However, in Atypical HUS patients, the platelets begin aggregating in
areas where they are not needed. These
tiny clots usually are not the same type of clots that can go to the heart or
the brain, because they are too small to do any damage there. But they are just the right side to get
caught in the renal system, thereby damaging the kidneys.
What are the symptoms of atypical HUS?
In most cases, Atypical HUS does not begin with a violent illness. Instead, the
patient starts off ill, fatigue, irritable, and lethargic to a point where
hospitalization is needed. Urine may be dark, due to an elevated BUN (Blood
Urine Nitrogen) count. The diagnosis of
the disease is actually quite easy to make if a simple blood test is
given. The blood test show damaged or
shattered red blood cells, a low red blood cell count, and a drastically
reduced platelet count.
What causes atypical HUS?
There are 3 major causation categories of Atypical HUS. Some cases of Atypical HUS seem to originate
from an external source. Pregnancy
induced Atypical HUS is the most common external source, but some forms of cancer,
HIV and other rare pneumonia diseases are a trigger for the disease.
A second major causal category are familial or genetic
cases. It has been demonstrated that a
sizable potion of the genetic cases (30%) are the result of a factor H
deficiency. Factor H is a protein that protects the tissues of the kidneys from
damage when clots form. Some of the
other cases appear to originate from a problem with the gene known as the
ADAMTS13 gene.
The third major causal category are
the idiopathic, or unknown cases. In
idiopathic cases, the disease seems to come out of nowhere. Genetic testing does not reveal any factor H
or an ADAMTS13 gene problem, and yet the patient has recurrent bouts with the
disease for no apparent reason. It is
believed that the unknown cases are probably traceable to a gene problem, but
that has not yet been proven.
What treatment is available?
There is no standard treatment, as each case is different. Children with Atypical HUS often develop various
complications, so therapy is tailored for each case, and tends to be supportive.
The symptoms are analyzed and a treatment plan is developed. Nephrologists have
tried drugs that interfere with clotting, drugs that interfere with platelet
function, blood transfusions, plasma infusions (plasma is the liquid part of
the blood), and plasmapheresis (a blood filtering
process). The best therapy is to closely monitor the disease, provide
supportive techniques to control blood pressure and minimized the damage to
kidneys though plasma and blood transfusions. Early dialysis may be life saving
until the kidney function is able to return to normal. Recurring cases must be
watched very closely, and immediate treatment should begin to prevent another
full blown HUS episode.
There is one important thing that you can do once you have
been diagnosed.
Be Proactive. Or more importantly, have
your doctor be proactive. Do not sit and
wait passively for the next attack to occur, and then rush to the hospital in a
panic effort to save the kidneys.
INSTEAD a) Find the initial
treatment that works b) Gradually, back
off that treatment, but only when the key numbers support backing off….for
example, it has taken us a full year to
back our plasma infusion down to once a week
c) Keep testing ….get on a
periodic plan to test your key numbers
(red blood cell count, platelet count, H & H, Hemoglobin and Hematocrit, BUN etc)
d) The first several times you
notice an illness coming on, get tested at the hospital for your key numbers
before your body has a total “crash”
What are the complications of atypical
HUS?
--Recurrence
--Kidney failure
--Seizures/Neurological problems
--No response to supportive treatments
--Return of HUS even after kidney transplant occurs
--Severe Hypertension (high blood pressure)
When
the kidneys fail is a transplant advisable?
Kidney failure is seen in 50% of patients with rejection
seen in 20-50% of those transplanted. It has been reported that in cases where
an unaffected sibling donates that the disease presents in the donor. Genetic
and factor H testing is
advisable to help with
deciding the best course of action.
What does all of this mean to a patient?
You must find a good hospital that is
proactive is monitoring your vital numbers.
Increasing knowledge about the pathogenesis and clinical associations
of thrombotic microangiopathies
(TMAs) has led to the realization that despite diverse
causes and clinical associations, this disorder shares similar clinical manifestations
with other conditions and it is hoped that by investing in TMA research all
its causes will benefit, especially atypical HUS which is very rare but devastating.
