Transcript follows. The letter was found at the blog of award-winning visual effects artist Doug Drexler.
Dear Mr Stewart
I am writing to thank you for all the pleasure that you gave my son [redacted] in your role as Jean-Luc Picard, Captain of the USS Enterprise.
For the past ten years [he] had been severely disabled by the inexorable effects of Duchenne Muscular Dystrophy - a disease that slowly degenerates all muscle tissue. [He] had great courage and refused to give in to his worsening disabilities. Inevitably his heart muscles became so weak that they could function no longer and [he] died peacefully on the evening of his 20th birthday, 30/12/91.
His great passion was Science Fiction and while a fan of the original "Star Trek" he greatly prefered "Star Trek The Next Generation". He had of course seen you before, as "Karla" in the Smiley stories, as "Sejanus" in I Claudius and of course as "Gurney" in Dune, I think he was quite bucked to see you as captain on the bridge of the Enterprise.
All through last year Wednesday evening was his highlight of the week, his excitement being matched only by his anger if "Star Trek TNG" was cancelled. I think that in his imagination he was there with you on the bridge, free of any disability, sharing to the full in all your adventures - he never missed one.
Please forgive me for writing to you this was but I felt that it was important for you to know that while "Star Trek TNG" might be regarded by some as trivial light entertainment it gives real pleasure and has great significance for others.
Once again my thanks for all the pleasure that you gave my son during his short life - and please, if you can, pass on my thanks to the remainder of the cast and everyone involved in the production of the programme.