HI
My name is Lea and I have Sickle Cell Disease.
Ever since I was born i was handled with the utmost care so as ot to "break"
This meant, I never was allowed to do anything crazy like swimming, hiking, standing in the sun, eating outside home etc. While sometimes I may look back and think "wow! my parents were crazy paranoid" , I always feel a sence of gratiude for the best they did with the information they had at that particular time.
When you have Sickle Cell, your body is compromised from the get go. What do i mean? Okay, its quite simple. Knowing the nature of the disease; the sickling , destruction of red blood cells, anemia, reduced supply of oxygen and not to mention the extra amount of work the body has to do to ensure proper growth and development with its very little and stretched resources, the body is left defenseless. From the first doctors visit, a dose of penicillin is prescribed to up those defenses. However, this still doesnt hide the fact that Sickle Cell Warriors are quite suceptible to infections.
From an article by Catherine Booth, Baba Inusa, Stephen K. Obaro on the International Journal Of Infectious Diseases , this is what I found out.
Infection is a significant contributor to morbidity and
mortality in sickle cell disease (SCD). The sickle gene confers an increased
susceptibility to infection, especially to certain bacterial pathogens, and at
the same time infection provokes a cascade of SCD-specific pathophysiological
changes. Historically, infection is a major cause of death in SCD, particularly
in children, and it was implicated in 20–50% of deaths in prospective group
studies over the last 20 years. Worldwide, it remains the leading cause of
death, particularly in less developed nations. In developed countries, measures
to prevent and effectively treat infection have made a substantial contribution
to improvements in survival and quality of life, and are continually being
developed and extended. However, progress continues to lag in less developed
countries where the patterns of morbidity and mortality are less well defined
and implementation of preventive care is poor. SCD increases susceptibility to infections and
the underlying mechanisms for susceptibility to specific pathogens.
Since you all know the clinical manifestations of SCD result
from two key processes: vaso-occlusion (blood vessel obstruction by sickled red
blood cells) and hemolysis (break down of red blood cells). Sickle cells, along
with non-sickled RBCs, leukocytes, and platelets, form cell groups, which
adhere to the vascular endothelium, causing obstruction of small blood vessels.
This tiny circulatory obstructions lead to acute and chronic tissue damage and
death, with multisystem effects, particularly in bone, lungs, brain, kidneys,
and spleen.
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| Causes of Infection in SCD #10003 |
Causes of Infection in Sickle Cell Disease
Impaired Spleen
Function
The spleen has a key role in the increased susceptibility to
certain bacterial infections seen in SCD. It functions as a phagocytic
(protective cells i.e. white blood cells) filter, removing old and damaged
cells and blood-borne microorganisms, and also produces antibodies. Individuals
with SCD typically suffer from reduced and in some cases, lack of splenic
function. The sluggish circulation through the spleen, high rates of O2
extraction, and local acidosis cause deoxygenation of HbS, promoting sickling,
which leads to congestion and swelling of the sinusoids of the spleen with
sickled cells. This can cause diversion of blood within the spleen, bypassing
the normal filtering mechanisms. Macrophages (large stationary white blood
cell) engulfing the abnormally shaped cells may become ‘blocked’, impairing
their phagocytosis (ingestion of bacteria) of other particles.
Individuals with SCD hence they cannot mount a rapid
specific response to captured organisms. Local infections can readily become
systemic and this, in combination with the loss of the spleen's filtering
function, can permit overwhelming sepsis (presence in tissues of harmful
bacteria and their toxins, typically through infection of a wound) to develop.
The main pathogen of concern is S. pneumoniae, though severe and systemic
infections with H. influenzae, Neisseria meningitidis, and salmonellae also
occur. Before preventive measures, children with SCD were 30–600 times more
likely to develop invasive pneumococcal disease (IPD), including pneumonia,
meningitis, and septicemia. Overwhelming sepsis can develop rapidly with no
obvious primary source of infection, resulting in shock, disseminated
intravascular coagulation, adrenal hemorrhage, and death within 24 to 48 hours.
Mortality can reach 35–50% from septicemia and 10% in meningitis. The risk is
confined almost exclusively to young children, with a reported incidence of 5.8
per 100 in children aged less than 3 years, 1.1 per 100 in those aged 5–9
years, and 0.6 per 100 in those aged over 10 years in the pre-treatment era.
While it is theoretically conceivable that children affected
by SCD in malaria hyper-endemic settings like Kenya may be at increased risk of
death from other pathogens such as malaria and invasive salmonellosis, poor
diagnostic facilities and the high childhood mortality rates call this
assertion into question. Well-planned longitudinal cohort studies to define the
etiologic agents that predominate in SCD morbidity and mortality in this region
are urgently needed.
Deficiencies in
Micronutrients
Zinc is known to be important for immune function, so low
levels in SCD have been suggested as a contributory factor in susceptibility to
infection. Zinc deficiency is associated with lymphopenia (abnormally low
levels of immune building white blood cells). Zinc deficiency may affect 60–70%
of SCD patients. High protein turnover increases requirements, while hemolysis
releases zinc, which is lost via the kidneys as renal tubular damage impairs
reabsorption. At the same time poor diet and inadequate intestinal absorption
could reduce intake. A study in 21 zinc deficient children suggested that
giving supplements reduced the incidence of bacterial infections and cut
hospital admissions.
Genetic Factors
Despite sharing the same underlying genetic mutation, the range
of severity in SCD patients is striking, with some patients disabled by
frequent crises and long-term complications while others live virtually normal
lives. Individuals are also differently predisposed to particular pathological
manifestations of the disease. This suggests that the SCD phenotype is multi-genic:
since many unlinked genes are involved in the underlying extreme processes in
SCD (such as destruction of sickled cells or endothelial adhesion), variation
in genes at multiple locus points may modify outcome. Complexities in a number
of genes involved in the immune response have been suggested as contributing to
increased susceptibility to infection in SCD.
Mechanical Factors
The pathological effects of SCD can themselves create an
environment supporting infection. Children with SCD are predisposed to
osteomyelitis (inflammation of bone/bone marrow). The bone marrow space is
expanded to accommodate the increased hematopoiesis (formation of blood/blood
cells) needed to compensate for chronic hemolysis (red blood cell destruction),
and oxygen demand is high. At the same time circulation is sluggish. Together
these factors render bone vulnerable to vaso-occlusive (obstruction of blood
vessel) episodes and infarction (tissue death). Areas of necrotic (dead) bone
act as focus for infection, which becomes established via hematogenous
(bloodstream) spread.
Edwardsiella tarda
is another enterobacterium that has been reported with increased incidence in
SCD. Increased gut permeability and biliary sludging in SCD is likely to be
responsible for this association. It may be that patchy ischemia and infarction
of bowel secondary to micro vascular occlusion permits gut bacteria to invade
the intestinal wall and enter the bloodstream.
Another consequence of micro vascular disease is its
association with acute chest syndrome. SCD carries an increased risk of
prolonged and severe respiratory infections due to Mycoplasma, Chlamydia and
other pathogens, particularly in children prone to pain or micro vascular sequestration,
such as those with SCD.
Finally, SCD patients may be predisposed to certain
iatrogenic (illness caused by medical examination or treatment) infections as a
result of therapeutic interventions. Blood transfusion is commonly used to
treat complications, particularly aplastic crisis or splenic sequestration
(when Hb falls acutely) and acute chest syndrome, priapism, or strokes (when
exchange transfusion is used to reduce the proportion of HbS). In general such
programs are potentially associated with increased risk of blood-borne
infections, particularly hepatitis B and C and HIV. Although all blood products
in developed countries are screened for these viruses, standards in other
countries may not be so exacting, so early hepatitis B immunization is recommended
as a preventive measure.
Now it is clear as day that my parents weren't crazy in being vigilant. As a sickle cell warrior speaking from experience, it is better to prevent than to treat. Sickle Cell is an expensive disease, however, it is way cheaper and less stressful to manage than to treat and bring the body back to balance when in crisis.
Next week we look at the effects of the infection on Sickle Cell Warriors and how we can prevent them. Until next time.
Love Life!
Lea
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