Clinical phenotype of the patient. (A) Magnetic resonance imaging (MRI) scans of the brain at 3.5 years (upper row), with arrowheads indicating (1) atrophy of the telencephalon, (2) arachnoidal cyst in the posterior fossa, (3) insufficient myelination, and (4) enlarged external and internal cerebrospinal fluid spaces. The lower row shows MRI scans of a healthy 3.5-year-old child. (B) X-ray of the pelvis showing flat, dyplastic acetabulae. (C) X-rays of the chest showing chronic interstitial pneumonia. (D) Neutrophil counts over time. Dashed line at 1000 neutrophiles/µL represents the clinical limit for neutropenia. (E) Bone marrow smear showing hypersegmented neutrophils.