The Case of Roberta Alden

Case study - The case of Roberta Alden

The Aldens are an African American family from a remote rural area. It is highly likely that Mr and Mrs Alden are distant relatives. When they moved to England they had seven healthy children, 4 boys and 4 girls. Their eighth child was a boy, who developed severe pneumonia at 3 months and died in hospital. An autopsy revealed that he had SCID. His thymus was immature, with only rare thymocyte and no Hassall's Corpuscles.

Two years later the Aldens had a daughter, who appeared healthy at birth but at 3 weeks old developed deeply pigmented spots on her trunk and face. 3 weeks later Mrs Alden noticed thrush in Roberta's mouth. The paediatrician aware of the family history ordered a chest X-ray and blood studies. No thymic shadow was seen. Her lymphocyte count was 0.15 x 109/L (normal >3 x109/L). Further investigation demonstrated her lymphocytes did not respond to phytohaemagglutinin (PHA) a non-specific T-cell mitogen. SCID was diagnosed.

HLA typing of Roberta and her siblings revealed an identical match, her brother. To test directly for histocompatibility a mixed lymphocyte reaction was performed - no reaction was seen. A bone marrow transplant was carried out which proved successful. 12 days post transplant Roberta's lymphocyte count had risen to 0.5x109/L, and the response of her lymphocytes to PHA had risen to half normal. A karyotype revealed that the responding cells were XY.