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?
All classes of immunoglobulin levels are reduced Lymph node biopsy shows depletion of follicles Both humoral and cell mediated immunity are affected It is caused by a mutation of the Btk gene