Detection of leukocyte adhesion deficiency type 1 in an infant by high-throughput targeted exome sequencing

Leukocyte adhesion deficiency type 1 (LAD-I) characterized by immune-deficiency and leukocytosis is rare in infant patients. A 43-day-old boy with severe leukocytosis, recurrent infections, defective wound healing and hepatosplenomegaly associated with an acquired cytomegalovirus infection. To establish the diagnosis definitively, a high-throughput targeted exome sequencing was performed, which yielded the diagnosis of LAD-I. A homozygous mutation in integrin subunit beta 2 (ITGB2), c.817G>A (p.G273R) was identified. Though LAD-I has been thoroughly-studied, with more than 300 detailed cases and 96 mutations in ITGB2, establishing a definitive diagnosis of LAD-I in infancy is challenging because of the lack of typical clinical presentations. Better understanding the molecular characterization of this disease is necessary to increase awareness and identification of infants with LAD-I.