A 7-month-old boy is brought to the clinic due to concerns for frequent infections. The patient has had 2 episodes of acute otitis media in the past month and developed bronchiolitis at age 5 months. The patient is developing normally and has received all age-appropriate vaccinations. Height and weight are at the 65th percentile. Cardiopulmonary examination is unremarkable. The abdomen is soft and nontender with no hepatosplenomegaly. There are red, scaly lesions over the cheeks bilaterally with some surrounding excoriations. Laboratory results are as follows: Which of the following is the most likely diagnosis in this patient?

Question

A 7-month-old boy is brought to the clinic due to concerns for frequent infections.  The patient has had 2 episodes of acute otitis media in the past month and developed bronchiolitis at age 5 months.  The patient is developing normally and has received all age-appropriate vaccinations.  Height and weight are at the 65th percentile.  Cardiopulmonary examination is unremarkable.  The abdomen is soft and nontender with no hepatosplenomegaly.  There are red, scaly lesions over the cheeks bilaterally with some surrounding excoriations.  Laboratory results are as follows:  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d62b_bc72_bc81_414878daf13c_MD0003_00 This infant's isolated low IgG and normal antibody response to vaccines are consistent with transient hypogammaglobulinemia of infancy (THI). In general, IgG in a newborn is maternally derived (ie, placental transfer of IgG to the fetus) and wanes after birth. A physiologic nadir in infant IgG levels occurs around age 3-6 months, at which time infants typically start to produce their own IgG, and levels begin to rise again. However, in patients with THI, IgG synthesis is delayed, and the physiologic nadir is prolonged beyond age 6 months. physiologic nadir Infants with THI may remain asymptomatic or develop recurrent infections (eg, acute otitis media, respiratory infections). Atopic features are also common and can include asthma, eczema, and food allergies. Leukocyte count is normal, and diagnosis is made based on an IgG level below normal for age. In some cases, IgA and/or IgM may be decreased as well. However, in contrast to common variable immunodeficiency, patients with THI generate a normal antibody response to vaccines, as seen here (Choice A). THI self-resolves, with normalization of IgG levels by early childhood. Most patients are managed with observation alone, but prophylactic antibiotics may be considered for recurrent infections. (Choice B) Severe combined immunodeficiency affects both T and B cells and presents with severe infections and failure to thrive in infancy. Leukocyte count and all immunoglobulins would be low. (Choice D) Wiskott-Aldrich syndrome is a genetic disorder characterized by eczema, recurrent infections, and microthrombocytopenia. This patient has a normal platelet count. (Choice E) X-linked agammaglobulinemia (ie, Bruton agammaglobulinemia) is a disorder of B-cell maturation in the bone marrow. Patients have B-cell deficiency with markedly low levels of all immunoglobulins and absent IgG response to vaccines. Educational objective: Transient hypogammaglobulinemia of infancy is a self-limited disorder characterized by low IgG (but normal leukocytes and antibody response to vaccines) due to prolonged physiologic nadir (age >6 months). Patients may be asymptomatic or have recurrent infections and atopic disease. References: Transient hypogammaglobulinemia of infancy. (http://www.ncbi.nlm.nih.gov/pubmed/31335076)

A 7-Month-Old Boy Is Brought to the Clinic Due to Concerns