Recurrent Infections and Suspected Immunodeficiency in Children
Children presenting with recurrent, severe, or unusual infections can be a diagnostic challenge for paediatric doctors. While most healthy children may experience 4 to 8 minor infections a year, particularly in nursery or school settings, a significant pattern of infections may signal an underlying immune disorder. The key is to distinguish between common childhood illnesses and a true immunodeficiency.
Red Flags and Clinical Clues
Paediatric doctors should have a high index of suspicion for an underlying immunodeficiency if a child’s infections fit the CRAMPS acronym:
Complicated or deep-seated infections (e.g., osteomyelitis, abscesses).
Resistant to standard antibiotic treatment.
Atypical organisms (e.g., Pneumocystis jirovecii, fungi).
Multiple locations of infection.
Persistent infections that do not resolve.
Severe infections requiring hospitalisation or intravenous antibiotics.
Other red flags include:
Two or more serious bacterial infections within a year.
Associated failure to thrive.
Infections with vaccine-preventable organisms.
A family history of immunodeficiency or early childhood deaths.
Delayed separation of the umbilical cord (>3 weeks), which can be a sign of a neutrophil disorder.
Aetiology
Immunodeficiency can be either primary (congenital) or secondary (acquired).
Primary Immunodeficiency: These are a group of inherited disorders. The age of onset can provide a clue to the type of disorder:
Onset <6 months: Suspect a T-cell disorder, such as Severe Combined Immunodeficiency (SCID).
Onset 6-12 months: May be a combined B- and T-cell disorder.
Onset >12 months: More likely a B-cell disorder (e.g., selective IgA deficiency).
Secondary Immunodeficiency: This is more common and can be caused by:
Chronic illnesses (e.g., diabetes, malnutrition, chronic kidney disease).
Malignancy or immunosuppressive treatments.
HIV/AIDS.
Down syndrome.
Clinical Assessment
History
A detailed history is paramount. Key questions include:
Nature of infections: What types of infections has the child had? Are they viral, fungal, or deep-seated skin infections?
Response to treatment: How often are antibiotics needed, and do they work?
Growth and development: Is the child thriving? Has their development been affected?
Immunisation history: Has the child received all their routine immunisations? Have there been any adverse reactions to a live vaccine (e.g., BCG abscess)?
Examination
A full physical examination is essential.
Growth: Plot height, weight, and head circumference on a growth chart.
Dysmorphic features: Look for any syndromic features associated with immunodeficiency (e.g., DiGeorge syndrome).
Lymph nodes: Assess the size of the lymph nodes and tonsils. A child with recurrent infections but tiny lymph nodes and tonsils may have an underlying B-cell disorder.
Skin: Examine the skin for eczema, granulomas, or pyoderma.
Other: Check for hepatosplenomegaly or any signs of systemic disease.
Investigations
Initial screening should be performed in all children with suspected immunodeficiency.
Initial tests: A full blood count with a differential is a key first step. Also, check immunoglobulins (IgG, IgA, IgM, IgE) and complement levels (C3, C4).
Antibody response: Assess the child’s antibody response to common vaccines like Tetanus, H. influenzae type B (HiB), and S. pneumoniae.
If these initial tests are abnormal or a specific disorder is suspected, further specialist tests are required in consultation with a paediatric immunologist:
Lymphocyte subset assay: This is a key test for diagnosing T-cell disorders like SCID.
Neutrophil function tests: To assess for phagocytic disorders like Chronic Granulomatous Disease.
Management
Management is based on the specific diagnosis and is always carried out in collaboration with a specialist immunology team.
Antibiotics: Children may require a higher dose of antibiotics or longer courses. Prophylactic antibiotics may also be necessary.
Vaccines: Live attenuated vaccines (MMR, Varicella, and BCG) should be avoided in children with suspected T-cell disorders.
Immunoglobulin therapy: Children with B-cell disorders may require regular immunoglobulin replacement therapy.
Specialist care: Referral to a paediatric immunology team is crucial. In some cases, a bone marrow transplant is the definitive treatment for severe primary immunodeficiencies like SCID.