REVIEWHereditary haemorrhagic telangiectasia: Pathophysiology, diagnosis and treatment
Section snippets
Overview of HHT
HHT, also known as Osler–Weber–Rendu syndrome,[1], [2], [3] is one of the most common disorders to be inherited as an autosomal dominant trait. Careful epidemiological studies reveal that it affects approximately 1 in 5000 individuals,[4], [5] with regional differences,6 and isolated communities displaying higher prevalences due to founder effects.[7], [8]
HHT was first described as a familial disease characterised by severe recurrent nasal and gastrointestinal bleeding with associated anaemia,
Histopathology
As in other telangiectatic states,89 the smallest HHT cutaneous telangiectatic lesion appears to be a focal dilatation of the post capillary venule in the upper horizontal plexus.90 Computer reconstruction of serial 1–2 mm sections suggest that the dilated post capillary venules enlarge, connect with dilated arterioles with loss of the intervening capillary bed, and form arteriovenous communications,90 associated with a lymphocytic perivascular cell infiltrate.90 Microscopic telangiectasia are
Management overview
Several helpful articles have been published in recent years guiding management practice. International HHT Guidelines published on line more than 12 months ago 32 were based on systematic assessments of the HHT publications up to October 2006. The 33 recommendations, representing the product of a fairly strenuous review process involving multiple experts, are a very helpful starting point for the field, and are presented in a separate column within Table 1.
The 2006–9 HHT evidence base
Clinical diagnosis
The mainstay of diagnosis remain the Curaçao Criteria, international consensus diagnostic criteria developed between 1997 and 1999 2 (Table 1), and recently validated.72 An individual has a diagnosis of “definite HHT” if three criteria are present; “suspected HHT” if two are present, and “unlikely HHT” if only one is present. A crucial issue for families and medical practitioners, is that no child of a patient with HHT can be informed they do not have HHT, unless they have been shown not to
AVMs
Details of the treatment of each type of AVM are beyond the scope of this text: the interested reader is referred to the references in Table 1, and recent treatment texts for general aspects of HHT [3], [32] and AVMs in cerebral,[68], [209], [210], [211] pulmonary,[57], [58], [59], [60], [61], [66], [105] hepatic[73], [74], [75], [76] and spinal[67], [68], [74], [75], [76] circulations.
Management of iron deficiency anaemia
In this chronic condition, it is essential to reserve treatments carrying higher risk, for patients with the
Perspective
For families with HHT, the recent advances in scientific and medical understanding of their condition are encouraging after the decades of limited advances. There are genuine hopes for improved and targeted treatment modalities, and emerging evidence that existing strategies are already offering affected individuals a better medical outlook than their grandparents.
Yet there are others for whom the deluge of new and frightening information holds concerns. As one attendee of the 2009 UK HHT
Conflict of interest statement
No conflicts of interest to declare.
Acknowledgments
The author thanks Dr. James Jackson, Dr. Alan Guttmacher and Dr. Fatima Govani for reviewing the manuscript; Katharine Thompson for bibliographical software assistance; and Professor John West for his framework of pulmonary circulatory concepts. She acknowledges support from the NIHR Biomedical Research Centre Funding Scheme, the British Heart Foundation, and British HHT families.
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