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Immunology 5 - Immunodeficiency (i) (Passive transfer of maternal IgG…
Immunology 5 - Immunodeficiency (i)
Classification
primary
genetic
no recognised cause
354 conditions
DiGeorge Syndrome
22q deletion
complete deletion = rare (total absence of thymus + B cells)
partial deletion more common
1 in 3000
incidence of other primary immunodeficiencies: 1 in 1000-5000
secondary
to another condition
recurrent bacterial infections
defects in humoral immunity
primary
IgA deficiency
only 1/3 will actually have problems (IgM can compensate)
1 in 300-500
most common
Specific Ig Deficiency
give a test vaccine - will fail to mount a specific response
poor epidemiology (1 in 1000-5000)
e.g. IgG subclass deficiency
subclasses 1,2,3 cause problems
x-linked agammaglobulinaemia
x-linked lymphoproliferative (XLP) syndrome
EBV susceptible
presents as hyperglobulinaema/lymphoma
Common variable immune deficiency (CVID)
known molecular cause in 20% of cases
Dx criteria: low IgG (>2 or below mean for age) AND low IgA/M
can't have Dx under 2 y/o as could be prolonged transient low IgG level
poor vaccine response
must rule out known causes of hypogammaglobulinaemia
onset: 2-80 y/o, often insidious, Dx often delayed , leading to bronchiectasis (irreversible scarring + dilation due to recurrent chest infections, present in 25% of cases when they receive Dx)
associated with granulomatous inflamm (esp in GIT) + malignancy
associated with autoimmunity due to disregulation - can be the presenting complaint + hardest thing to treat - may have to use immunosuppressants
decreased life expectancy (esp with complications @ time of Dx) - need to increased awareness + Dx earlier
other complications: atrophic gastritis, pernicious anaemia, hepatosplenomegaly, lymphadenopathy, Fe 2+ deficiency
25% have no complications
defective Ig production
secondary
thymoma
lymphoma
CLL (B cell malignancy)
myeloma (plasma cells malignancy)
post-splenectomy (usually mild)
drugs
chemo (e.g. cyclophosphamide knocks out B cells)
rotuximab (monoclonal Ig)
Ig loss
diarrhoea
bleeding
urine (kidney disease)
not usually a problem as tissue levels are still normal
physiological
deficient B cells
Recurrent viral infections + PCP
deficient T cells
Recurrent S aureus (boils + abscesses)
deficient neutrophils
recurrent meningococcal disease
C5-9 complement deficiency (no MAC)
Passive transfer of maternal IgG
occurs in last trimester
transient; falls by 6-9 months old
transient low level until baby synthesises their own IgG
Baby can make IgM in utero if immune system stimulated - but shouldn't happen
IgA doesn't cross placenta
starts being produced from birth + levels rise v slowly (adult levels by 12-15 y/o)
premature babies (under 38 wks) won't have reached optimal maternal IgG levels - elongated transient low level
poor placental function also affects IgG transfer - baby won't grow well (seen on US)
Managing humoral defects
minor: antibiotics + vaccination
significant
Iv then subcut Ig replacement
agressive management of infections (prolonged courses of antibiotics)
chest physiotx
bronchodilators