Case Studies
Case 3.4 Severe combined immunodeficiency
David was born at full term after a normal pregnancy; his parents were first cousins. He was not given BCG at birth. He was well until 2 months when he became 'chesty' and needed antibiotics. Routine immunizations were postponed until he had recovered but he then developed 'antibiotic-related' diarrhoea, which did not settle after the antibiotics were stopped. After 3 months a further chest infection occurred, his weight fell from the 25th centile to below the third. He was admitted for investigation of his failure to thrive.
On examination, he was a thin, scrawny infant on the 25th centile for length. There were no rashes or lymphadenopathy but his liver was palpable just below the right costal margin. He had slight tachycardia and tachypnoea. Investigations (Table C3.4) showed a marked deficiency of T cells with normal numbers of B cells, although no immunoglobulin production. He had a T- B+ form of severe combined immune deficiency, and was referred promptly to a specialist unit for bone marrow transplantation.
Table C3.4 Immunological investigations* in Case 3.4.
| Full blood count |
| Haemoglobin |
108g/l |
| Neutrophil count |
3.5 x 109/l |
| Lymphocyte count |
0.7 x 109/l [3-15] |
| Microbiology results |
| Blood |
Negative for HIV by PCR |
| Urine |
Negative for cytomegalovirus |
| Nasopharyngeal swab |
Rhinovirus |
| Stool |
Echovirus-22 |
| Sputum |
Negative for bacterial culture and pneumocystis PCR |
| Immunological results |
| IgG |
0.9g/l |
| IgA |
<0.1g/l |
| IgM |
0.1g/l |
| Lymphocytes |
| CD3+/CD4+ |
0.09 x 109/l |
| CD3+/CD8+ |
0.04 x 109/l |
| CD19+ |
0.23 x 109/l |
| CD3-/CD16+56+ |
0.31 x 109/l |
| CD4+/CD25+ |
0.08 x 109/l |
| CD3+/HLA-DR+ |
0.11 x 109/l |
|
Lymphocyte stimulation assays |
|
SI** |
CD69*** |
|
patient |
control |
patient |
controls |
| Phorbol ester and ionophore |
6 |
300 |
<1% |
49 |
| Phytohaemagglutinin |
4 |
385 |
<1% |
29 |
| Antiserum to CD3 |
3 |
165 |
<1% |
17 |
*Normal range for 3 months shown in brackets.
**Stimulation index.
***Percentage of CD3+ cells expressing CD69 after 6 hours - mean of controls.
|
