A 14-month-old boy is brought to the office for follow-up due to pneumonia. The patient required hospitalization 2 weeks ago for lobar pneumonia, his second admission for this diagnosis in the past 6 months. A chest tube was placed for an effusion, with the pleural fluid demonstrating minimal leukocytes and numerous gram-positive cocci in clusters. The fever resolved after 10 days, after which the patient was discharged, although he continues to have cough and occasional increased work of breathing. This slow symptom improvement also occurred with an episode of nonpurulent staphylococcal cellulitis last month. Temperature is 37.7 C (99.9 F). Oral examination reveals eruption of both upper central incisors with surrounding erythema and ulceration. The posterior oropharynx appears unremarkable. Lung sounds are diminished at the left lower base with some scattered crackles. Heart sounds are normal. The abdomen is soft and nondistended without hepatosplenomegaly. The remainder of the examination is unremarkable. Laboratory results are as follows: Chest x-ray reveals opacification of the left lower lobe and a small left effusion improved from 2 weeks ago. Which of the following is most likely present in this patient?

Question

A 14-month-old boy is brought to the office for follow-up due to pneumonia.  The patient required hospitalization 2 weeks ago for lobar pneumonia, his second admission for this diagnosis in the past 6 months.  A chest tube was placed for an effusion, with the pleural fluid demonstrating minimal leukocytes and numerous gram-positive cocci in clusters.  The fever resolved after 10 days, after which the patient was discharged, although he continues to have cough and occasional increased work of breathing.  This slow symptom improvement also occurred with an episode of nonpurulent staphylococcal cellulitis last month.  Temperature is 37.7 C (99.9 F).  Oral examination reveals eruption of both upper central incisors with surrounding erythema and ulceration.  The posterior oropharynx appears unremarkable.  Lung sounds are diminished at the left lower base with some scattered crackles.  Heart sounds are normal.  The abdomen is soft and nondistended without hepatosplenomegaly.  The remainder of the examination is unremarkable.  Laboratory results are as follows:  Chest x-ray reveals opacification of the left lower lobe and a small left effusion improved from 2 weeks ago.  Which of the following is most likely present in this patient?

Quizplus · Accepted Answer

11ec25c8_d628_881a_bc81_c1be55323662_MD0003_00 This patient with recurrent, nonpurulent infections and marked neutrophilia most likely has leukocyte adhesion deficiency (LAD). LAD is an autosomal recessive disorder characterized by reduced CD18 antigen on the surfaces of neutrophils. CD18 is a key component of integrins, which are required for neutrophil migration through vascular endothelium to the site of infection. Because the skin and oral mucosa are susceptible to bacterial invasion, LAD classically causes recurrent skin (eg, cellulitis) and mucosal (eg, gingival erythema, ulceration) infections; gastrointestinal and respiratory tract (eg, pneumonia) involvement can also occur. Infections may be prolonged, as seen in this patient, and are often life-threatening. Because neutrophils cannot travel to the site of infection, the absence of purulence is typical, and infectious fluids (eg, pleural effusion) lack leukocytes. Other characteristic features of LAD include impaired wound healing, which can manifest as delayed separation of the umbilical cord (age >3 weeks) and delayed wound healing after surgery or trauma. The most common pathogens in LAD are Staphylococcus aureus, as in this patient, and gram-negative bacilli. Characteristic laboratory findings include peripheral leukocytosis and neutrophilia because white blood cells cannot exit the vessels. (Choices A and C) Giant cells with bilobed nuclei in germinal centers are characteristic of Hodgkin lymphoma, and increased peripheral myeloblasts are typical of acute myeloid leukemia (AML). Although these malignancies can predispose to recurrent infections, they would not explain the minimal inflammatory cells seen in this patient's infectious pleural effusion. In addition, hepatosplenomegaly and elevated lactate dehydrogenase are often present, particularly with AML, and neutrophilia would not be expected with either condition. (Choice B) A low CD4 cell count, as seen in HIV infection, results in severe bacterial, viral, and fungal opportunistic infections and failure to thrive. Leukocytosis and neutrophilia are not consistent with this diagnosis. (Choice D) The presence of giant granules within neutrophils is pathognomonic for Chédiak-Higashi syndrome, a lysosomal trafficking disorder characterized by recurrent infections, oculocutaneous albinism, and neurologic abnormalities. This patient has no hypopigmentation, and neutropenia (not neutrophilia) would be expected. Educational objective: Leukocyte adhesion deficiency is due to a defect in CD18 antigen on neutrophils, which leads to impaired neutrophil migration. Patients have recurrent, nonpurulent skin and mucosal infections; impaired wound healing; and leukocytosis with neutrophilia. References: Leukocyte adhesion deficiencies. (http://www.ncbi.nlm.nih.gov/pubmed/23351991)

A 14-Month-Old Boy Is Brought to the Office for Follow-Up