Abstract: FR-PO311

Clinical Diagnosis of Senior Loken Syndrome in a Patient with SDCCAG8 Mutation Genetically Diagnosed as Having Bardet-Biedle Syndrome

Session Information

Category: Genetic Diseases of the Kidney

  • 801 Cystic Kidney Diseases

Authors

  • Fujii, Yuko, Osaka Medical College, Takatsuki, Osaka, Japan
  • Tamai, Hiroshi, Osaka Medical College, Takatsuki, Osaka, Japan
  • Ashida, Akira, Osaka Medical College, Takatsuki, Osaka, Japan
  • Matsumura, Hideki, Osaka Medical College, Takatsuki, Osaka, Japan
  • Shirasu, Akihiko, Osaka Medical College, Takatsuki, Osaka, Japan
  • Yamazaki, Satoshi, Osaka Medical College, Takatsuki, Osaka, Japan
  • Nakakura, Hyogo, Osaka Medical College, Takatsuki, Osaka, Japan
  • Morisada, Naoya, Kobe Univ. Graduate School of Medicine, Kobe, Japan
  • Iijima, Kazumoto, Kobe Univ. Graduate School of Medicine, Kobe, Japan
  • Hattori, Motoshi, Tokyo Women’s Medical University, Tokyo, Japan
Background

Both Senior Loken Syndrome (SLS) and Bardet-Biedle Syndrome (BBS) are ciliopathies. SLS is characterized by retinitis pigmentosa (RP) and familial nephronophthisis, leading to end-stage kidney disease. BBS is characterized by six major symptoms: RP, polydactyly, obesity, genital abnormalities, learning difficulties, and renal defects. So far, ciliopathy has been diagnosed according to phenotypes, but now it is often diagnosed by genetic testing using techniques such as next-generation sequencing. Here we describe a patient who was clinically diagnosed as having SLS but in whom genetic testing indicated BBS.

Methods

The patient was diagnosed as having RP at the age of six years. She had learning disability, preobesity and dyslipidemia, but no polydactyly. When she was eight years old, she was diagnosed as having chronic kidney disease, anemia, and liver dysfunction. Kidney and liver biopsy revealed renal tubule cysts, tubule membrane disruption, and liver fibrosis. Therefore, SLS was diagnosed but no mutation in NPHP1 was detected. Peritoneal dialysis was started at the age of nine years, and the patient underwent kidney transplantation with a graft from her father at the age of fourteen years. At the age of twenty years, she again underwent genetic testing for most of the mutations associated with ciliopathy. This revealed that she had a homozygous mutation in intron 11 of the SDCCAG8 gene which had caused a frameshift mutation.

Conclusion

SDCCAG8 is known to be one of the causative genes related to SLS and BBS without polydactyly. The fact that the patient had learning disability, preobesity and dyslipidemia suggested a high probably of BBS. Although these symptoms are not specific, she did not have the typical symptom of BBS including polydactyly. Therefore, a definitive diagnosis of BBS was difficult without any information concerning genetic mutation. As only a few cases of SDCCAG8 mutation have been reported previously, accumulation of further cases will help to clarify the characteristics of the phenotype of SDCCAG8 mutation, thus contributing to the better management of patients with ciliopathy.