In addition to the TNXB gene, another potentially important gene that might be associated with the hypermobile Ehlers-Danlos syndrome was identified in October 2016.

The results were published by a group of NIH researchers who have long been involved in mast cell research.

It is well known that a significant portion of hEDS patients also suffer from mast cell activation syndrome (MCAS) and dysautonomia (often POTS). Scientists have tried to find the common ground for this complex of disorders, but so far none succeeded.

Recently, the group of Prof. Milner published their results, which perhaps led to the identification of one gene causing those three conditions:

The gene TPSAB1 (Tryptase alpha/beta 1)

Source: LYONS, Jonathan J., et al. Elevated basal serum tryptase identifies a multisystem disorder associated with increased TPSAB1 copy number. Nature Genetics, 2016.

It was found that duplication or triplication in TPSAB1 was present in 35 families, who had already had an increased basal tryptase in previous studies. This gene encodes the enzyme alpha tryptase, which is a mast cell-specific marker.


Furthermore, one could observe that all subjects suffered from POTS and connective tissue symptoms on top of the mast cell-typical symptoms.

The more copies of alpha tryptase that were present, the higher the basal serum tryptase in the blood of the affected people was, and the more severe symptoms the patients showed.

Patients without changes in TPSAB1 may also experience the presence of the EDS-MCAS-POTS combination. However, if  the basal serum tryptase is increased, which can be easily measured, one might think of the possibility of testing this newly identified gene. At this point, such a change is still of unknown significance for the individual because research on that topic just started.

Like with TNXB, TPSAB1 might be the underlying cause for only a small amount of EDS patients. However, it offers the opportunity for further studies and more answers.