Characteristics of the clinical presentation — HHT · Osler’s disease

Hereditary hemorrhagic teleangiectasia (HHT) may be classified as a form of arteriovenous malformation (AVM), and yet the condition has features that do not fit seamlessly with those of other AV malformations. For example, the small, “young” lesions of the nasal mucosa in HHT do not yet have high blood flow and do not clinically have the characteristics of an AV shunt. These develop at a later stage in their individual history. The transformation from an “Osler spot”, a small vessel ectasia, to a high blood flow shunt occurs at varying rates at many locations in the nose. The dynamic depends on factors that are elusive and, to date, inadequately described. What is known is the influence of hormonal changes in the body. The increased dynamic that the disease undergoes during puberty and pregnancy is striking.

In addition to the genetic component underlying the vascular changes, the mechanical stress of nasal breathing leads directly and indirectly to injury of the mucosa and thus to the development of the disease spots.

The development of the nasal spots and especially the bleeding tendency are triggered by the mechanical stress of the turbulent airflow – “second hit” (see section on genetic basis). The observation that mechanical trauma, but also stress from UV light, can lead to the formation of lesions raises significant questions regarding current therapeutic measures with laser and coagulation. Since 85% of patients report suffering more from the disease as they age, it is difficult to resolve these issues. The natural progression of the disease is certainly difficult to differentiate from influences of therapy using the methods of evidence-based medicine.

The influence of the aerodynamic trauma in the nose, which is necessary for formation of the bleeding foci provides the basis for the peculiar therapeutic principle of nasal occlusion.