Diseases of B cell Defiency Flashcards
What age range might you expect a B cel deficiency?
1-3 years old, first 2-9 months the baby has moms IgG
What class of microorganisms would expect to be most problematic in a patient with a B cell deficiency?
Extracellular bacteria (CD4 and B cells)
What is causing the abnormality in this CXR of this 2 yo?
In younger children, bacterial pneumonia frequently has a very round, well-defined appearance on chest radiography, simulating a mass. This is referred to as round pneumonia and is most common in children younger than 8 years of age. Round pneumonia is more common in the lower lobes and is most often caused by Streptococcus pneumoniae infection. The reason this appearence in children is thought to be due to underdevelopment of collateral pathways of air circulation. IN the apporpriate clinical setting in a child with cough and fever, a lung mass senn on chest x-ray should be conisdered round pneumonia, and additional CT imaging is not indicated. Follow up x-ray should be obtained several weeks after antibiotic therapy to ensure resolution. After 8 years of age however, if a round mass is seen on chest radiograph, other pathology should be considered.
A patient gets febrile, tachycardic, tachypneic patients gets a CBC.
Abnormal results are increased WBC.
Differential shows only increased neutrophils and bands. Lymhs are normal
-Ig levels are all below normal levels
What are you thinking it is?
Lymphocytes are normal because this is B cell related and T cell are more abundant in lymphocyte number.
- Low Ig levels of all rules out selective IgA
- age rules out CVID (normally presents in 20s-30s)
- This is most likely X-linked agammaglobulinema
What causes X-linked agammaglobulinemia?
Defect iin BTK, a Bruton tyrosine kinase gene
- leads to no B-cell maturation. X-linked recessive, more common in boys
- leads to recurrent bacterial and enteroviral infections after 6 months of age (due to maternal IgG prior to that)
decrese in Ig of all classes
abesnt B cells in peripheral blood
abesnt/scanty lymph nodes and tonsils
-sequencing genes is required to identify the actual BTK mutation
Where is B-cell development does a BTK mutation arrest development?
Arrest development at the pre-B cell stage. At this point it is past the pro-b cell stage and has a pre-BCR. the problem is a mutation in BTK prevents BCR signaling so it is arrested as pre-B cell because it is unable to signal that is has a BCR
What is used to treat DIC?
Antithrombotic therpay to prevent clots from DIC
What kind of microorganisms are normally cleared by the spleen?
Blood bourne.
Often encapsulated bacteria like pneumococcus
A febrile patient with cultures of pneumococcus and a removed spleen. What immune parameters are most likely imparied in this patient?
Pneumococcus is encapsulated in the blood, so it is important for the macrophages in the spleen to present to B cells in the marginal zone.
Problem is he does not have a spleen so there is no presentation and no Ig to the pneumoccocus is made.
-Impaired are Pneumococcus-specific IgG2
After splenectomy, what else should the patient receive?
Conjugated vaccines to make a T-dependnet response.
What is the most important treatment for patients with B cell deficiencies?
IVIg to help prevent infections.
What is type II Hyper IgM caused by?
Type II is a B-cell deficiency due to a mutation in the AID gene, which is essential for Ig class switching.
Type I is a T cell defiency due to mutant or abest CD40L (on T cells), therefore cannot induce B cells to class switch
A patient presenting with petechial hemorrhages in the palpebral conjuctivae is suggestive of what?
Bursting of BVs as a result of intrinsic clotting (DIC)
Differentiate lab results for
XLA, Hyper-IgM, Asplenia, Ig deficiency, CVID
What are these called and what are they indication for?
Howell-Jolly Bodies
- usually seen in asplenia or reduced spleen function (should be cleared by the spleen)
- can also be seen in anemia due to high rate of RBC formation in this situation
