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Immune Disease A-B | |||||||||||||||
is a genus of
parasitic nematode worms. One species,
A. suum, typically infects pigs, while another, A. lumbricoides,
affects human
populations, typically in sub-tropical and tropical areas with poor
sanitation.
This infection is known as ascariasis. Adult
A.lumbricoides and A.suum live in the small
intestine. A female A.lumbricoides can produce up to 200,000 eggs a
day, though
the number of eggs produced per female worm is lower when there are
large
number of worms present in the gut, a phenomenon called density
dependent
fecundity. When an egg is passed into the environment it develops into
a third
stage larva in about 10 days, the rate depending on the temperature and
relative humidity. This typically takes place on the soil, which is why
A.lumbricoides is classified with Trichuris trichiura and the hookworms
Necator
americanus and Ancylostoma duodenale as soil-transmitted helminths. It
is
estimated that some 1.2 billion people are infected with A.lumbricoides. Infections with
A.lumbricoides occur by the accidental
ingestion of mature, embryonated eggs, typically in food or on fingers.
The egg
hatches in the intestine, penetrates the mucosa and passes via the
portal blood
vessels to the lungs. There the larva breaks out into the alveoli and
is
coughed up and swallowed. If large numbers of larvae are present this
can cause
verminous pneumonia. The larvae then pass though the stomach again and
grow to
become adult worms in the small intestine. A female A.lumbricoides can
grow up
to 40 cm long and weigh 9 g. An adult male worm is about half the
weight of a
female and up to 30 cm long. Large numbers of worms can accumulate in
the
intestine which can cause intestinal obstruction, or they can migrate
into the
bile duct or pancreatic duct and cause obstruction there. The
distribution of worms among hosts is typically
high aggregated, so that the majority of people have light infections
while a
small proportion have moderate to heavy infections. The distribution of
A.lumbicoides and many other intestinal helminths is empirically best
described
by the negative binomial distribution. The heaviest infections with
A.lumbricoides are typically found among children of school-age (5 - 14
years). is a chronic
illness involving the respiratory system
in which the airway occasionally constricts, becomes inflamed, and is
lined
with excessive amounts of mucus, often in response to one or more
triggers.
These episodes may be triggered by such things as exposure to an
environmental
stimulant (or allergen), cold air, warm air, moist air, exercise or
exertion,
or emotional stress. In children, the most common triggers are viral
illnesses
such as those that cause the common cold.This airway narrowing causes
symptoms
such as wheezing, shortness of breath, chest tightness, and coughing.
The
airway constriction responds to bronchodilators. Between episodes, most
patients feel well but can have mild symptoms and they may remain short
of
breath after exercise for longer periods of time than the unaffected
individual. The symptoms of asthma, which can range from mild to life
threatening,
can usually be controlled with a combination of drugs and environmental
changes. Public
attention in the developed world has recently
focused on asthma because of its rapidly increasing prevalence,
affecting up to
one in four urban children. Ataxia
telangiectasia Ataxia-telangiectasia
(AT) (Boder-Sedgwick syndrome or
Louis-Bar syndrome) is a primary immunodeficiency disorder that occurs
in an
estimated incidence of 1 in 40,000 to 1 in 300,000 births (Lederman,
2000). Symptoms and
prognosis Telangiectasias
are small, red 'spider' veins. These
typically appear on the surface of the ears and cheeks or in the
corners of the
eyes in patients with AT. The 'ataxia' part of the name refers to the
difficulty patients with AT have walking. At an early age, the child's
walking
becomes wobbly; at teens, handicapped-bound; and at the early 20s, the
condition becomes fatal. In some cases the victim gets enlarged bowels, and they don't feel like eating. AT is characterized ve
cerebellar
ataxi, oculocutaneous telangiectasia, progressive cerebellar
dysfunction,and
recurrent sinopulmonary infections secondary to progressive
immunological and
neurological dysfunction. AT patients are significantly predisposed to
cancer,
particularly lymphomas and leukemia. Other manifestations of the
disease
include sensitivity to ionizing radiation, premature aging, and
hypogonadism.[citation needed] AT has been a major interest of
scientists since
the 1960's because it may yield an insight into numerous other major
health
problems, such as cancer, neurological disease, immunodeficiency, and
aging
(Lederman, 2000). Cause Nijmegen
breakage syndrome (NBS), also known as ataxia
telangiectasia variant 1, is a very rare syndrome which could be
considered as
a differential diagnosis to AT. People with Nijmegen breakage syndrome
show the
same immunodeficiency, radiosensitivity and risk of cancer as AT but do
not
have any ataxia or oculo-cutaneous telangiectasia. Nijmegen breakage
syndrome
sufferers also show microcephaly. The gene associated with Nijmegen
syndrome
(Nbs1) is known to be located on 8q21. Interestingly,
the proteins expressed by the hMre11
and Nbs1 genes exist in the cell as a complex, along with a third
protein
expressed by the hRad50 gene. This complex, known as the MRN complex,
plays an
important role in DNA damage repair and signalling and is required to
recruit
ATM to the sites of DNA double strand breaks. Mre11 and Nbs1 are also
targets
for phosphorylation by the ATM kinase. Thus, the similarity of the
three
diseases can be explained in part by the fact that the protein products
of the
three genes mutated in these disorders interact in common pathways in
the cell. In the early
ataxic stages children may be diagnosed
with cerebral palsy. Other
differential diagnoses are: Ataxia
oculomotor apraxia type 1 Ataxia
oculomotor apraxia type 2 Gaucher disease
Hartnup disease
Niemann-Pick
disease Refsum disease Clinical
Description Diagnostic
Methods Diagnosis is
usually achieved by examination and
identification of both ataxia and oculo-cutaneous telangiectasia. This
is then
followed by laboratory tests for low levels of IgA, IgG2, IgG4, and
IgE.
Sufferers may also have a low lymphocyte count and other immunological
abnormalities. This can then be followed by cytogenetic and molecular
testing
to confirm the diagnosis. MRI and CT scans may show signs of cerebellar
atrophy. Etiology Mutations in
the ATM gene are thought to come in two
types: Null mutations
are those which cause complete loss of
function of the protein and are therefore inherited in a recessive
manner and
cause AT. ‘Missense’
mutations which produce stable, full sized
protein with reduced function e.g. substitutions, short in-frame
insertions and
deletions etc. These mutations act by dominantly interfering with the
normal
copy of the protein. The majority of AT sufferers, 65-70%, have truncating mutations, with exon skipping mutations being particularly common. This results in very low or undetectable levels of ATM protein. Missense mutations are the most common type of mutation found in carriers with breast cancer. Individuals with two missense mutations are believed to have a milder form of AT, which may account for cases of attenuated AT. Therefore it is thought that ‘subtle constitutional alterations of ATM may impart an increased risk of developing breast cancer and therefore act as a low penetrance, high prevalence gene in the general population’ (Maillet et al 2002). Autism Autism is
highly heritable, although the genetics of
autism are complex and it is generally unclear which genes are
responsible. In
rare cases, autism is strongly associated with agents that cause
birth defects. Other proposed causes, such as
childhood vaccines, are controversial and the
vaccine hypotheses lack convincing scientific
evidence. Most
recent reviews estimate a prevalence of one to two
cases per 1,000 people for autism, and
about six per 1,000 for ASD, with ASD averaging a 4.3:1 male-to-female
ratio.
The number of people known to have autism has increased dramatically
since the
1980s, at least partly due to changes in diagnostic practice; the
question of
whether actual prevalence has increased is unresolved. Autism affects
many parts of the brain; how this
occurs is poorly understood. Parents usually notice signs in the first
two
years of their child's life. Early behavioral or cognitive intervention
can
help children gain self-care, social, and communication skills. There
is no
cure. Few children with autism live independently after reaching
adulthood, but
some become successful, and an autistic
culture has developed,
with some seeking a cure and others
believing that autism is a condition rather than a disorder. Burnout is a
psychological term for the experience of
long-term exhaustion and diminished interest (depersonalization or
cynicism),
usually in the work context. It is also used as an English slang term
to mean
exhaustion. Burnout is often construed as the result of a period of
expending
too much effort at work while having too little recovery, but it is
sometimes
argued that workers with particular personality traits (especially
neuroticism)
are more prone to experiencing burnout. Further, it appears that
researchers
disagree about the nature of burnout. While many researchers argue that
burnout
refers exclusively to a work-related syndrome of exhaustion and
depersonalization/cynicism, others feel that burnout is a special case
of the
more general clinical depression or just a form of extreme
fatigue/exhaustion
(thus omitting the cynicism component). Health care
workers are often prone to burnout. Cordes
and Doherty (1993), in their study of employees within this industry,
found
that workers who have frequent intense or emotionally charged
interactions with
others are more susceptible to burnout. Still, burnout can affect
workers of
any kind, including students at the high school and college levels. High stress
jobs can lead to more burnout than normal
ones. Taxicab drivers, law enforcement personnel, air traffic
controllers,
musicians, teachers, lawyers, emergency service workers and high
technology
professionals seem more prone to burnout than others]. General
practitioners
seem to have the highest proportion of burnout cases (according to a
recent
Dutch study in Psychological Reports, no less than 40% of these
experienced
high levels of burnout). The most
well-studied measurement of burnout in the
literature is the Maslach Burnout Inventory. Maslach and her colleague
Jackson
first identified the construct "burnout" in the 1970s, and developed
a measure that weighs the effects of emotional exhaustion,
depersonalization,
and reduced sense of personal accomplishment. This indicator has become
the
standard tool for measuring burnout in research on the syndrome. People
who
experience all three symptoms have the greatest degrees of burnout,
although
emotional exhaustion is said to be the hallmark of burnout. Although
burnout is work-related, most responsibility
for burnout currently rests on the individual worker in the United
States.
Other countries, especially in Europe, have included work stress and
burnout in
occupational health and safety standards, and hold organizations (at
least
partly) responsible for preventing and treating burnout. Burnout is now
being studied in its reported
antitheses, job engagement. The word is
also used as pejorative slang, referring
to an individual who has burned themselves out on a vice, such as drugs
or
alcohol. It may also refer to an individual who has "burned out" his
or her interest in life, similar to a slacker. Citation |
