You are diagnosing a female patient with repetitive pyogenic (= pus-forming) bac

Question

You are diagnosing a female patient with repetitive pyogenic (= pus-forming) bacterial infections. Her lab tests show elevated levels of serum IgM, but pathologically low concentrations of IgG and IgA. What could be a possible explanation of this clinical situation? Assess each statement (26-31) as either factually correct (= true) or incorrect (= false) in the context of the above-given description:

26. A mutation of the gene coding for uracil-DNA glycosylase.

27. A defect in B-cell TLR expression that impairs the T-independent pathway of B-cell activation.

28. A mutation of the gene coding for activation-induced cytidine deaminase.

29. A mutation of the gene coding for CD40.

30. A mutation of the gene coding for CD40 ligand.

31. A mutation of the gene coding for hypoxanthine-guanine phosphoribosyltransferase.

Explanation / Answer

The patient is suffering from hyper IgM (HGIM) syndrome. They are suceptible to recurrent ans severe infections. There is increased risk of cancer as well. These patients have inability to switch from IgM antibody production tp other antibodies like IgG and IgA. So, IgM levels in blood are markedly elevated.

The most common HIGM syndrome is X-linked and due to mutations of CD40 ligand in CD4+ T lymphocytes. Mutations of CD40, the receptor for CD40L, cause a rare autosomal form of HIGM. Mutations of Activation-Induced Cytidine Deaminase (AICDA) and Uracil (DNA) Glycosylase (UNG), both expressed by follicular B lymphocytes, lead to defective class switch recombination and somatic hypermutation. Mutations of Nuclear Factor B Essential Modulator (NEMO), an X-chromosome associated gene, result in hypohidrotic ectodermal dysplasia and immune deficiency.

T cell independent B cell activation requires TLR. So, defect in TLR expression in B cells will impair T cell independent B cell activation. A mutation of the gene coding for hypoxanthine-guanine phosphoribosyltransferase will result in Leych-Nyhan syndrome or gout.

Considering all these, statements from 26 - 30 are true and the statement 31 is false.

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.