HAVE YOU ANSWERS THE QUESTION: WHAT IS THE BEST INITIAL TEST FOR WORK-UP FOR IMMUNODEFICIENCY? CHECK THE ANSWERS of MCQS Published on 2/9/2019

MCQ# 01

Correct Answer: B

The initial step in the workup of a child with a suspected immunodeficiency should always include a complete blood count and differential, as this test will reveal disorders involving lymphopenia (particularly T-cell lymphopenias) and neutropenia. Other hints can be found by the CBC, including small platelets associated with the Wiskott–Aldrich syndrome, anemias, and evidence of eosinophilia.

An erythrocyte sedimentation rate is a nonspecific marker of inflammation and would not point to a specific immunodeficiency. While quantitative immunoglobulins, peripheral T-cell phenotyping, and lack of antibody response to standard immunizations would all be part of an immunodeficiency investigation, these would not be considered first steps in the evaluation.

MCQ#02

Correct Answer:E

This patient has Omenn syndrome, caused by abnormalities in the RAG1/2 lymphoid-specific recombination activating genes. This condition leads to failure of both T-cell and B-cell development and subsequent severe combined immunodeficiency. The presence of erythoderma and eosinophilia are clues to this diagnosis, which is not associated  with neutrophilia. Macrocytosis, while seen in disorders of folic acid metabolism, is not seen in this disorder. Basophilic stippling is characteristic of sideroblastic anemia or lead toxicity. Small platelets are found in the Wiskott–Aldrich syndrome, but not in the Omenn syndrome.

MCQ#03

Correct Answer:C

The severity of recurrent infection can be a clue for an underlying immunodeficiency. While children in daycare are frequently ill with viral upper respiratory tract infections, over 3 hospitalizations for severe bacterial infection should raise concern for a larger immune-mediated dysfunction. Absence of tonsillar tissue, adenoidal tissue, or thymic tissue, either by direct visualization or on radiograph may be a clue to an underlying B-cell or T-cell dysfunction. Hypertrophy of these tissues, in contrast, is not uncommon in immunocompetent children. Failure to thrive can also be a sign of an underlying

immune dysregulation, but this child was growing and maintaining his height and weight, not crossing percentiles, as would be seen in a failure to thrive.

MCQ#04

Correct Answer:D

This patient’s history of chronic and recurrent infection and failure to thrive raises suspicion for an underlying immunodeficiency. The accompanying features of severe eczema, hepatosplenomegaly, and petechiae point towards a diagnosis of Wiskott–Aldrich syndrome. Wiskott–Aldrich syndrome is an X-linked disorder characterized by eczema, increased risk of infection, and small platelets with thrombocytopenia.

There is no particular effect on either numbers of neutrophils or red cell volumes. The underlying cause of WAS is a mutation in the WASP (Wiskott–Aldrich syndrome protein) gene, leading to abnormalities in intracellular signal transduction. Patients with WAS are at high risk for hematologic malignancy, but the presence of lymphoblasts on peripheral smear would not be the most common finding seen in the disorder.

MCQ#05

Correct Answer:B

Hyper-IgE syndrome has both an autosomal dominant and autosomal recessive form. The autosomal dominant form includes eczema, skeletal and vascular abnormalities, while both forms display the immunologic defects, including elevated levels of IgE, increased risk of viral infections and autoimmunity. Impairment of neutrophil chemotaxis leads to failure to migrate to the site of infection and therefore lack of a local inflammatory response, such as erythema, warmth, or release of cytokines leading to production of a fever.

Impaired intracellular killing of organisms leading to granuloma formation is not a feature of Job syndrome, nor is eosinophilia or antibody cross-linking abnormalities.