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My name is Fernando Nieto Chillaron and I would like to tell you a little bit of my story. I am diagnosed with Glycogenin-1 Deficiency, also known as GSD15. It affects the skeletal muscle and more seriously the muscle of the heart.


Fernando Nieto Chillaron




Glycogenin-1 Deficiency – GSD15


Age 41


Age 44



I am 44 years old and I live in Bétera, in the Valencia region of Spain. I am diagnosed with an ultra rare disease that my doctors call Cardiac Glycogenesis Type XV. IamGSD uses the term GSD15.

Unusual amongst muscle GSDs

It is unusual amongst the muscle GSDs, as it is one of the few which results in the profound depletion of glycogen in the cardiac and skeletal muscles, whereas most GSDs leave an excess of glycogen.

I was finally diagnosed at the age of 41, after several years searching for a diagnosis, when they did a heart biopsy and saw that I had unusual deposits in the walls of my heart.

High-tech monitoring

Currently my symptoms are as follows: muscle weakness, daily dizziness, instability and cardiac arrhythmias. 

I have a Holter monitor implanted subcutaneously (under the skin) in my chest. This monitors the electrical signals from my heart. These are sent continuously to the hospital where the arrhythmias which I suffer are reported. They can control the device remotely.

The condition seems to be progressive

My heart is inflamed by the abnormal deposits and, little by little, those deposits are going to increase. There is as yet no treatment to stop this process.

The only known case of GSD15 in Spain.

A little heart failure

I am starting to have a little heart failure – my heart not being able to pump as well as it should. I am currently taking an anticoagulant (blood thinner), because one of the effects of the atrial area of my heart not pumping strongly is to create blood clots. In 2018 I suffered a stroke in the cerebellum (the part of the brain at the back of the skull which coordinates and regulates muscular activity). Luckily I recovered quite well.

Further investigations

At the moment the doctors are considering doing a biopsy of skeletal muscle, since I have been suffering from pain in my limbs. These pains are becoming increasingly strong. The biopsy should reveal whether I have abnormal deposits in my skeletal muscle as well as in my heart.


GSD15 is so rare that I understand that I am the only affected person in Spain. IamGSD has so far only heard of four cases worldwide, including mine. Surely there must be more?

I am looking forward to one day being able to exchange experiences with another person with GSD15. If that is you, please email me on:

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