From Usher syndrome to Bardet-Biedl syndrome: Diagnosis after an atypical presentation

Syndromic associations of kidney and ophthalmological diseases are not typical in the young adult. The most common kidney manifestations are malformations of the genitourinary apparatus, while some syndromes can also present with kidney parenchymal disease. We report on a 51-year-old woman evaluated in the nephrology clinic for 12 months due to abnormal kidney function. She had been diagnosed with Usher syndrome due to the development of retinitis pigmentosa and sensorineural hearing loss in the last 20 years, without genetic testing. She had a family history of parental consanguinity, and disperse cardiac disease, congenital malformations, and congenital deafness. For chronic kidney disease of unknown etiology, a kidney biopsy was performed which revealed focal segmental glomerulosclerosis (FSGS) of the perihilar variant. This diagnosis prompted genetic testing that identified a mutation on gene SDCCAG8: c.397G>T, known for causing Bardet-Biedl type 16 and Senior-Løken type 7 syndromes. This case of perihilar FSGS is atypical in the setting of a ciliopathy and absence of metabolic or cardiovascular risk. Though urinary tract malformations and kidney disease can be expected, glomerular disease is not described in the literature. Genetic syndromic diagnoses require genetic screening due to the overlap of different symptoms and variable penetrance. The diagnosis of genetic diseases requires a high degree of suspicion, especially when the phenotype of the kidney disease is unusual. Identification of variants can help identify individuals who can benefit from genetic counseling.