Snapshot A 4-day-old girl born to a G1P1 mother with no complications presents with a fever. There is some swelling with serosanguinous fluids around her rectum. Cultures from the fluid grow Staphylococcus spp and is treated with antibiotics. On day 15 of life, she develops an ear infection and is once again treated with antibiotics. The umbilical cord is still attached, and on day 34 of life, the umbilical stump is noted to be erythematous, indurated, and tense. A completel blood cell count is significant for leukocytosis. Immunoglobulin levels are normal. Flow cytometry reveals decreased expression of CD18 to < 1%. Introduction Primary immunodeficiency resulting from phagocytic dysfunction Genetics autosomal recessive absence or defective CD18 Epidemiology very rare primarily seen in pediatric population Pathogenesis defect in LFA-1 integrin (CD18) protein on leukocytes normal physiology CD11a/CD18 (LFA-1 integrin) expressed on lymphocytes are important in the trafficking and adhesion to vascular endothelium interactions with antigen presenting cells cytotoxic T-cell killing results in impaired migration and chemotaxis Prognosis 75% of individuals have severe disease, with typically < 1% expression of CD18 may succumb to life-threatening infection within 1-2 years of life mild disease, with 1-30% expression of CD18 survive to adulthood Presentation Symptoms delayed separation of umbilical cord at birth to > 30 days omphalitis recurrent infections of skin and mucosa most commonly due to Staphylococcus spp., enteric gram-negative bacteria, and fungi perirectal and labial cellulitis otitis media absent pus formation serosanguineous fluids may be present impaired wound healing poorly formed, thin, bluish scars gingivostomatitis Evaluation ↑ Neutrophils in the absence of infection dramatically ↑ with infection Histology localized infection with absence of neutrophils or pus edema and necrosis Flow cytometry absence of CD18 on leukocytes Differential Diagnosis Chédiak-Higashi syndrome Chronic granulomatous disease Treatment Hematopoietic stem cell transplant high success rate Prophylactic antibiotics Complications Life-threatening infections Graft versus host disease after stem cell transplant