Hereditary haemorrhagic telangiectasia, also known as Osler–Weber–Rendu disease, is a rare dominantly inherited disease. It is a distinct clinical entity described by Sir William Osler [ 1] at the turn of the century, in terms of its clinical features, telangiectasis and the familial occurrence.
Only a few studies describing the epidemiology of the disease have been reported. The prevalence of HHT has previously been estimated to be between 2.5 and 19.4 per 100 000 [ 2–6]. Between one- and two-thirds of HHT patients will seek medical advice on treatment [ 7].
Clinical characteristics and genetics of HHT
In HHT patients, telangiectatic lesions are often present in the oral mucosa and the nasal mucosa, and leads to epistaxis in 90% of patients and occasionally also to oral bleeding [ 3, 8]. Epistaxis beginning in the teenage years is the first symptom in the majority of HHT patients [ 3, 7, 8]. Telangiectatic lesions in the gastrointestinal tract cause symptoms in 20–30% of patients [ 9]. With age, this complication may result in severe anaemia, and a high requirement for transfusion in later life is not uncommon [ 10, 11].
Pulmonary arteriovenous malformations (PAVMs) and cerebral arteriovenous malformations (CAVMs) represent other severe manifestations of the disease [ 12, 13]. Patients with one or both of these complications risk early death from rupture of the malformations. In particular, these complications may be fatal during pregnancy [ 14, 15]. However, studies on mortality rates in patients with HHT have been very scarce.
During the last few years, the genetics of HHT have been studied extensively. Currently, at least two different chromosomal loci have been implicated. In HHT type 1, mutations at chromosome 9 alter the coding sequence of endoglin [ 16, 17]. In HHT type 2, mutations at chromosome 12 alter the coding sequence of the activine receptor-like kinase 1 (Alk 1) [ 2, 18]. In both types, the mutations impair blood vessel growth and repair, but it has recently been established that patients with HHT 1 more frequently develop PAVMs than those with HHT 2 [ 19, 20].
Objectives of the present study
The aim of this study was to establish the prevalence of HHT as of 1 January 1995 and to compare this with the prevalence as of 1 January 1974 in the County of Fyn, Denmark. In parallel, a long-term follow-up study of the initial patient sample was carried out in order to study the mortality in HHT patients.