Primary Immunodeficiencies (PIDs) Flashcards
Describe the Adenosine Deaminase (ADA) deficiency form of SCID.
T-, B-, and NK-. Leads to accumulation of toxic by-product deoxyadenosine.
Describe the Purine Nucleoside Phosphorylase (PNP) deficiency form of SCID.
T-, B-, and NK+/-. Leads to accumulation of intracellular deoxyguanosine triphosphate (dGTP). Antibody levels are unchanged. Characterized early onset neurological abnormalities and autoimmune disorders. Can be treated with HSCT.
Describe the Artemis deficiency form of SCID.
T-, B-, and NK+. Characterized by radiosensitivity. Infant presents with diarrhea, candidiasis, and pneumocystis jiroveci, and increased risk of lymphomas. Can be treated with HSCT.
Describe the RAG1/RAG2 deficiency form of SCID.
T-, B-, and NK+. Leads to impaired V(D)J recombination. Infant presents with diarrhea, candidiasis, and pneumocystis jiroveci. Can be treated with HSCT.
Describe the Omeen Syndrome form of SCID.
A form of RAG1/RAG2 deficiency SCID that retains partial function of RAG1/RAG2. Characterized by severe erythroderma, splenomegaly, eosinophilia, and high IgE. Can be treated with HSCT.
Describe the Jak3 deficiency form of SCID.
T-, B+, and NK+. Leads to defect in IL-2 receptor signaling. Low levels of serum Ig. Can be treated with HSCT.
In primary agammaglobulinemia, at what point is the developing B cell typically arrested in? What kind of mutation usually causes it?
Typically arrested in the pre-B cell stage. Usually caused by X-linked trait, but autosomal recessive forms also exist.
Describe the BTK deficiency form of agammaglobulinemia.
B-, T+, and NK+. Caused by X-linked mutation, leading to a defect in rearrangement of Ig heavy chain. Serum antibodies are typically totally absent or very low. Can be treated with HSCT.
Describe Isolated IgG Subclass deficiency.
B+, T+, and NK+. Patients are usually asymptomatic but may be associated with recurrent infections. IgG subclasses, such as IgG2, are low but IgM/IgA/IgE are normal.
What point of B cell maturation is affected by an IgA deficiency?
Terminal differentiation, mature B cell converting to a plasma cell.
Describe IgA deficiency.
B+, T+, and NK+. Characterized by recurrent infections, may be asymptomatic. Very common, most affected patients are healthy.
How can an IgA deficiency cause anaphylaxis during an IVIG treatment?
Patients with undetectable IgA levels may have serum anti-IgA IgG which can lead to anaphylaxis in response to IVIG treatment.
Describe DiGeorge Syndrome (DGS).
T-, B+, and NK+. Caused by microdeletion of 22q11.2 region, leading to a T cell deficiency. Characterized by classic triad: cardiac anomalies, hypocalcemia, and hypoplastic thymus. Humeral immunity is usually intact.
Describe Hyper IgM (HIGM) Syndromes. What are its two main causes?
B+, T+, and NK+. Can be caused either by an X-linked CD40L deficiency (2/3), or an autosomal CD40 deficiency (1/3). B cell is unable to perform class switching or somatic hypermutation. Cannot produce plasma B cells. Can be treated with HSCT.
Describe transient hypogammaglobulinemia of infancy.
B+, T+, and NK+. Occurs when intrinsic Ig production is delayed for up to 36 months. Leads to low IgG and IgA concentrations but IgM may be normal or low. Ig concentrations normalize between 2-4 years.