Case Report: Decade long Cysteamine Therapy for Intermediate Cystinosis

Intermediate cystinosis, a rare lysosomal storage disorder, poses diagnostic challenges due to its diverse clinical presentations and slower progression compared to nephropathic cystinosis. This condition affects roughly 5% of cystinosis cases and can lead to end-stage kidney disease (ESKD) if diagnosis and treatment are delayed. Unlike other types, intermediate cystinosis may not present with classic symptoms like Fanconi syndrome or ocular manifestations, making diagnosis challenging. Additionally, the management of this condition can be complicated, as cystine-depleting medications such as cysteamine are difficult for many patients to tolerate due to complex administration requirements and side effects. The report details a case of intermediate cystinosis successfully managed with a decade-long course of cysteamine treatment.

Daisuke Katagiri, Center Hospital of the National Center for Global Health and Medicine (NCGM), Tokyo, Japan, and colleagues described the case of a patient who initially showed urinary abnormalities at age three during a routine health examination for children—a screening unique to Japan. Cystinosis was confirmed when the patient turned 12, leading to the initiation of cysteamine therapy and regular monitoring of cystine levels.

Despite persistent proteinuria, the patient's renal function advanced slowly. Two renal biopsies revealed multinucleated podocytes and cystine crystals but no focal segmental glomerulosclerosis. Throughout the treatment, the patient's renal function remained stable.

In this case, the patient was initially diagnosed with cystinosis at age 12, based on symptoms including Fanconi syndrome, proteinuria, and corneal cystine deposits. Cysteamine treatment commenced and was maintained for ten years. Two renal biopsies conducted during this period revealed multinucleated podocytes and cystine crystals, confirming the diagnosis. Despite persistent proteinuria, renal function remained stable, showcasing the efficacy of long-term cysteamine therapy.

Intermediate cystinosis often lacks the hallmark symptoms of nephropathic cystinosis and can be difficult to diagnose. A specific health screening for 3-year-olds in Japan enabled early detection in this patient, which was crucial for successful treatment. Cysteamine remains the only effective treatment, though it is challenging to administer due to side effects and its distinctive odor. Continuous treatment and adherence are essential for improving outcomes and delaying complications.

"Our case underscores the importance of early diagnosis and sustained cysteamine therapy in managing intermediate cystinosis. While the use of renal biopsies in ongoing treatment is rare, our findings suggest they are valuable for monitoring disease progression and treatment efficacy. Further research is needed to understand the implications of multinucleated podocytes and their relationship to glomerular damage in cystinosis," the researchers concluded.

Reference:

Kawamura, M., Katagiri, D., Yamamoto, Y. et al. Intermediate cystinosis: a case report of 10-year treatment with cysteamine. BMC Nephrol 25, 275 (2024). https://doi.org/10.1186/s12882-024-03722-8