A 1 year old boy is brought to the OPD by his parents with complaints of inability to gain weight and chronic diarrhoea. He was growing well till the age of 6 months. After that, he staed to develop recurrent episodes of pneumonia. Family history is positive for similar symptoms in a maternal uncle. On examination, he is below the 3rd percentile for weight. Tonsils are absent. Stool is positive for Giardia. Which of the following is not true regarding his condition?: (A) All classes of immunoglobulin levels are reduced, (B) Lymph node biopsy shows depletion of follicles, (C) Both humoral and cell mediated immunity are affected, (D) It is caused by a mutation of the Btk gene
Answer is C. This childs presentation suggests X-linked or Bruton&;s agammaglobulinemia. It is primarily a disease of humoral immunity. Cellmediated immunity is not affected. Bruton Agammaglobulinemia Bruton agammaglobulinemia is an inherited immunodeficiency disease caused by mutations in the gene coding for Bruton tyrosine kinase (BTK). B cells do not differentiate and mature. They are arrested in the pre B cell stage. There&;s extremely low IgG levels (below 100 mg/dL) and absence of other immunoglobulin classes. The tonsils and lymph nodes are usually atrophic. Lymph node biopsy reveals depletion of cells of B cell-dependent areas - The follicles. Babies born with this disorder have viually no peripheral B cells (<1%) and suffer from recurrent bacterial infection Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition