Chapter 9, Problem 15Q

Summary Introduction

Case summary:

A patient, age 6 months reported with pneumonia caused by Pneumocystis jirovecii, which upon further immunological investigations diagnosed as X-linked hyper-IgM syndrome (XHIGM).

Characters in the case:

Anthony Hoffnagle, the patient under evaluation.

Adequate information:

The patient reported frequent episodes of pneumonia, septic arthritis, and febrile convulsion. Investigations were carried out that showed neutropenia with normal B-cell and T-cell counts but elevated IgM and remarkably low IgG and IgA compared to the reference ranges. Further bone marrow aspiration studies showed severe maturational arrest of the myeloid lineage at the promyelocyte-myelocyte stage. As a treatment, he was suggested of long term intravenous immunoglobulin prophylactic antibodies and periodic injections of granulocyte colony stimulating factor (G-CSF) for episodic neutropenia.

To Determine:

The genetic mutation defect involved in X-linked hyper-IgM syndrome (XHIGM).