Transient Hypogammaglobulinemia of Infancy

Etiology

There exact cause of transient hypogammaglobulinemia of infancy is unknown. Proposed mechanisms include 1) malfunctioning T cells that fail to stimulate the appropriate synthesis of antibodies by B cells, 2) suppression of IgG production by maternal IgG, 3) low production of critical cytokines, and 4) genetic variations in families prone to immunodeficiency.[3][4][5]

Epidemiology

The estimated frequency of transient hypogammaglobulinemia varies between studies.  In some studies, it is the most common IgG deficiency in childhood.[6] Research has described it worldwide, and it is thought to be highly underdiagnosed due to variations in the criteria for diagnosis.  THI has been reported to be more common in males.  More than half of the patients are diagnosed by the age of one year and the remaining after the age of five years.  Initial low IgM and IgA levels were associated with slow recovery. Patients with longer duration of breastfeeding recover earlier.[7]

Pathophysiology

Transient hypogammaglobinemia of infancy may represent an exaggerated physiologic nadir when maternal IgG begins to decrease and before the child begins to synthesize their own immunoglobulin.  Although the mechanism is not fully elucidated, the presence of maternal immunosuppressive antibodies (IgG) crossing the placenta, that disrupt the humoral immune system of the neonate is one suggestion. This inhibition can cause a reduced level of not only IgG but also IgM and IgA, as seen in some cases.  

Some studies indicate that patients with THI have a normal number of B lymphocytes but a transient impaired function of T-lymphocytes associated with immunoglobulin synthesis. It stresses the importance of B and T cell cooperation to result in a proper immune response.[1]

History and Physical

In transient hypogammaglobulinemia of infancy, most patients experience upper and lower respiratory tract infections and allergic disorders, to include food allergies. More severe manifestations include urinary tract infections, gastroenteritis, and invasive infections.  Physical exam findings are consistent with the specific type of infection.

Typical symptomatic presentations include [2][3][4]:   

• Sinus pulmonary infections
• Bacteremia
• Meningitis
• Otitis media
• Arthritis
• Septicemia
• Bronchiectasis
• Recurrent tonsillitis
• Pyodermitis
• Purulent conjunctivitis
• Failure to thrive
• Aphthous stomatitis 
• Diarrhea
• Loss of weight   
• Recurrent abscess      
• Loss of weight 
• Autoimmunity
• Atopy
• Sinus pulmonary infections
• Viral infections
• Neutropenia
• Persistent vomiting
• Fungal infection (candidiasis)

Some infants remain asymptomatic with a diagnosis following immunologic evaluation for other reasons or family history.

Evaluation

The laboratory investigation of a patient with transient hypogammaglobulinemia of infancy includes the assessment of both immunoglobulin levels, B-cell quantitative assessment, antibody testing, immunophenotyping, and T cell function and he and other studies as follows[5][6][7][8]: 

Quantitative Serum Immunoglobulins

• IgG
• IgM
• IgA
• IgG1
• IgG2
• IgG3
• IgG4

In THI, IgG is at least two standard deviations below expected controls.[9] IgA and IgM may or may not present as decreased.

Antibody Activity

Detection of isohemagglutinins (IgM)

• Anti-type A blood
• Anti-type B blood

IgG antibodies (post-exposure)

• Rubella
• Measles
• Varicella Zoster

IgG antibodies (post-immunization)

• Tetanus toxoid
• Diphtheria toxoid
• Pneumococcal polysaccharide
• Polio

Most infants with THI produce normal antibodies to vaccines including diphtheria, tetanus, hepatitis A and B vaccines, conjugated Haemophilus influenzae type B, measles, mumps, and rubella vaccines. In the U.S., most children receive the conjugated pneumococcal vaccine, and they respond well. If a patient fails to respond to an immunization such as tetanus, a thoroughly immunological study should be done to diagnose an early immunodeficiency disorder.

Other assays

• Serum protein electrophoresis

Blood Lymphocyte T Subpopulations

• Total lymphocyte count
• T lymphocytes (CD3, CD4, and CD8)
• CD4/CD8 ratio

B-cell Quantitative Assessment

• Levels of CD19
• Levels of CD20
• Levels of CD21
• Levels of CD81
• Levels of CD 225

T cell and B cell function reports as normal in most studies.

Microbiological Studies

• Cerebrospinal fluid (culture, chemistry, and histopathology)
• Blood culture
• Stool culture
• Sputum examination

Other Investigations 

• DNA testing 
• Complete blood cell count   
• Chest x-ray
• Diagnostic ultrasound
• CT scan

Other tests may be necessary as clinically indicated to exclude other causes.

Treatment / Management

Medical Care

Transient hypogammaglobulinemia of infancy treatment is conservative.

• Antibiotic treatment with prophylactic antibiotics is reasonable if children begin to experience infections.
• In patients who develop severe life-threatening infections or recurrent respiratory tract infections despite antibiotic therapy, a trial of antibody replacement therapy in the form of intravenous immunoglobulin (IVIG) is indicated.
• If allergic rhinitis occurs, treat with topical nasal corticosteroids and antihistamines.
• Routine immunizations should be performed, including a conjugated heptavalent pneumococcal vaccine for routine immunization in children beginning at age 2 months. [10][11][12][13][10]
(B2)

Surgical Care

Due to the frequency of ear infections, the placement of tympanostomy tubes should be considered. Functional endoscopic sinus surgery (FESS) for chronic sinusitis may also be a consideration.

Differential Diagnosis

Differential diagnosis of transient hypogammaglobulinemia of infancy includes:

• X-linked (Bruton) agammaglobulinemia: recurrent bacterial infections affect boys, and genetic studies may reveal the presence of Bruton tyrosine kinase (BTK) mutations).[14]
• Common variable immunodeficiency: recurrent bacterial infections usually later in life (second-fourth decade).  Diagnosis is verified once all causes of immunodeficiency have been ruled out.[15]

Prognosis

The prognosis of transient hypogammaglobulinemia of infancy depends on the severity of the immunodeficiency.  The prognosis for those who are symptomatic or present with mild disease is good with no significant morbidity.  Patients with severe disease may be affected with opportunistic infections, atopy or autoimmunity, and have a more complicated course but, by definition, THI should completely resolve. Few patients may present a condition similar to X-linked agammaglobulinemia and must receive treatment with antimicrobials and IVIG for life.

Complications

Complications of transient hypogammaglobulinemia of infancy include[16]:

• Fungal infections including oral candidiasis 
• Bacteremia
• Premature death
• Anaphylaxis 
• Chronic diarrhea
• Neutropenia
• Food Allergies