Snapshot
- A 2-month-old baby boy is brought in for an urgent visit to the pediatrician. He has had several ear infections in his short lifetime and now seems to be struggling with a cold. On physical exam, his tongue is noted to be coated with white film. His scalp and face are covered with a flaky dandruff-like substance. Immediately concerned, his pediatrician orders a chest radiograph, which shows absence of thymic shadow. Flow cytometry is ordered.
Introduction
- Combined B- and T-cell disorder causing immunodeficiency
- Life-threatening disease of recurrent infections
- Pathogenesis
- multiple variants found
- most common is X-linked defective common gamma chain
- found in IL-2R, IL-4R, and IL-7R
- defective T-cell activation
- autosomal recessive adenosine deaminase deficiency
- ↑ deoxyadenosine, which is toxic to lymphocytes
- ↓ DNA synthesis
- autosomal recessive JAK3 deficiency
- B-cells
- decreased immunoglobulin production
- T-cells
- markedly decreased T-cells
Presentation
- Symptoms
- symptoms present < 3 months of age
- failure to thrive
- recurrent bacterial, viral, fungal, and protozoal infections
- chronic diarrhea
- Physical exam
- eczematous dermatitis
- erythroderma (> 90% body surface area involvement)
- severe seborrheic dermatitis
- diffuse alopecia
- eczematous dermatitis
- absent lymphatic tissue, including tonsils and thymus
Evaluation
- Diagnosis often delayed due to maternal IgG protecting baby in first few months of life
- ↓ Lymphocyte count (< 3000/μL)
- Chest radiography with no thymic shadow
- Flow cytometry
- absent T-cells
- abnormal function of B-cells
Differential Diagnosis
Treatment
- Bone marrow transplant
- life-saving treatment
- no concerns for allograft rejection
- Gene therapy
Prognosis, Prevention, and Complications
- Prognosis
- without intervention, death by 2 years
- patients < 6 months of age who receive transplant have the best outcomes
- Complications
- severe infection
- death