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Familial lupus anticoagulants
I J Mackie1, C B Colaco, S J Machin
1Department of Haematology, Middlesex Hospital Medical School, London.
Insights
Investigating lupus families revealed that prolonged KPTT, indicating lupus anticoagulant (LA), was common even in healthy relatives. Anticardiolipin antibody levels did not consistently correlate with LA severity, suggesting environmental factors in lupus-like disorders.
Area of Science:
- Hematology
- Immunology
- Genetics
Background:
- Systemic lupus erythematosus (SLE) and lupus-like diseases can present with coagulation abnormalities.
- Lupus anticoagulant (LA) is an autoantibody associated with increased thrombotic risk.
- The familial occurrence of SLE suggests potential genetic or environmental influences.
Purpose of the Study:
- To investigate coagulation abnormalities in families with multiple members affected by SLE or lupus-like disease.
- To assess the prevalence of lupus anticoagulant (LA) and anticardiolipin (CL) antibodies within these families.
- To explore potential environmental or transmissible factors contributing to lupus-like disorders.
Main Methods:
- Global coagulation tests, including dilute thromboplastin, Russell's viper venom, and thermal stability/absorption assays.
- Radioimmunoassay (RIA) for anticardiolipin (CL) antibodies.
- Investigation of three families with multiple affected members.
Main Results:
- Eleven out of 19 individuals had SLE or lupus-like disease; 8 showed evidence of LA with prolonged KPTT.
- Five of the 11 affected individuals had high anticardiolipin titres.
- Prolonged, non-correctable KPTTs were observed in healthy relatives (spouses and siblings) without bleeding or thrombotic history.
- No close correlation was found between KPTT length and anticardiolipin titre.
Conclusions:
- Unexplained prolonged KPTT in routine screening may indicate LA, potentially in asymptomatic individuals.
- The presence of LA and prolonged KPTT in healthy family members suggests non-genetic factors, possibly transmissible agents or environmental influences, may play a role in lupus-like disorders.
- Anticardiolipin antibody levels may not be a reliable indicator of LA severity or risk.
Abstract:
Three families having more than one affected member with SLE or lupus-like disease were investigated by global coagulation tests as well as methods based on dilute thromboplastin, Russell's viper venom and thermal stability/absorption, and by RIA for anticardiolipin (CL) antibodies. Of the 19 persons, 11 had SLE or lupus-like disease. Eight of these 11 had a prolonged KPTT and other evidence of LA, while only 5/11 had high anticardiolipin titres. Four healthy spouses of affected females, and three asymptomatic siblings also had prolonged non-correctable KPTTs. These persons had no bleeding or thrombotic history and normal clotting factor levels. Further clotting tests were negative, although one had raised anti-CL antibody. Such cases may account for some of the patients one finds during routine haemostatic screening with unexplained prolonged KPTT. Although anticardiolipin levels are raised in subjects with LA, there was no close correlation between length of KPTT and anticardiolipin titre. These findings would support a hypothesis of transmissible agents or other environmental factors being involved in lupus-like disorders.