Rare Diseases and Kidney Stones: Are Stones in Amino Acid Transport Disorders Special?

OBJECTIVES: Amino acid transport disorders (atd) include the cystine storage disease, De-Toni-Debré-Fanconi complex, Hartnup disease, Lowe's syndrome, cystinosis, and cystinuria. All of them are inherited and very rare diseases. Some cause kidney stones, especially cystinuria, which is thought to be responsible for 1% of all stones in adults. Little is known whether kidney stones of atd patients are treated differently. Thus, we analyzed German reimbursement data to find out about possible variations.

METHODS: Reports from German DRG-Institute (InEK) and Statistical Office (DESTATIS) for 2021 were analyzed for hospital kidney stone treatments in patients with atd to compare with all treatments for kidney stones. Analysis was performed with Microsoft-Access® 2019.

RESULTS: 102,518 (all) cases with main diagnosis kidney stone were coded in 2021, 90 of them with atd. Average age of atd patients was 26.5 years (median 22y), all patients 52.3 years (median 52y). 62.2% male atd patients (all: 67.4%). Length of stay was 2.9 days in atd (all: 2.5 days). Kidney stones were found in atd: 73.3% (all: 38.0%); ureter stones in 11.1% of atd (all: 51.4%); kidney and ureter stone simultaneously in 15.6% of atd (all 9.5%). Urogenital implants coded in 22.2% of atd (all: 19.0%). The ureterorenoscopic (URS) lithotripsy was the leading procedure with atd: 61.7% (all: 21.7%). Holmium laser was used in 34.4% of atd (all: 12.2%).

CONCLUSIONS: Kidney stones of atd patients are different. Patients are much younger, have much less ureter stones, but longer hospitalization. Advanced techniques like Holmium laser are more frequently applied, preferred pathway is URS lithotripsy. Less than the expected stones due to cystinuria were coded.