Pictured on the left is Bob Cratchit and his crippled son, Tiny Tim, two beloved characters from Charles Dickens' A Christmas Carol. In this fun 1992 article by the pediatrician D.L. Lewis, the case is made that Tiny Tim suffered from renal tubular acidosis.
So what's the evidence? Dickens describes Tim's illness as being a syndrome of short stature, asymmetric crippling, and intermittent spells of weakness. The book also implies that there is some medical treatment available for this illness (which the Cratchits are initially unable to afford given the tight-fisted nature of Cratchit's boss, Ebeneezer Scrooge), and without such treatment Tim would be condemned to death within the year. Fortunately, after his encounters with the Ghosts of Christmas Past, Present, and Future, Scrooge is able to reverse his selfish ways, supplying Cratchit with a much-welcomed bonus with the implication that Tiny Tim will now be able to afford said medical treatments and survive.
The author of the above article performed a review of available pediatric textbooks within the time frame of the book's setting (1830s-1850s) and determined that the likely treatment regimen for Tim's condition would involve alkali-containing compounds such as sodium bicarbonate and sodium citrate, along with potassium repletion and vitamin D repletion. A distal (Type I) RTA would fit nicely with these symptoms as his crippling could potentially seen as osteomalacia with pathologic fractures (the skeleton can develop severe weakness in the setting of prolonged acidemia), his spells of weakness could potentially be explained by hypokalemic muscle weakness, and his impending death could potentially be explained by the resultant renal failure that could result from chronic nephrocalcinosis, another aspect of RTAs.
Another possibility would simply be that Tiny Tim suffered from severe vitamin D deficiency and resultant rickets--a relatively common affliction during this time period.
The more recent "real-life" Tiny Tim--the absurdist ukulele player--did not have kidney problems to my knowledge.