Senior-Løken syndrome with IQCB1/NPHP5 mutation in an adult: a case report

Senior-Løken syndrome is a rare autosomal recessive ciliopathy characterized by nephronophthisis and early-onset retinal dystrophy. It is typically diagnosed in childhood, and adult-onset diagnosis is rare and may delay renal-protective interventions. Here, we report a rare case of Senior-Løken syndrome in an adult with an IQCB1/NPHP5 mutation.

A 20-year-old Turkish male presented with rotatory nystagmus since birth, progressive visual impairment from childhood, and chronic kidney disease that began during adolescence. The patient exhibited polyuria and polydipsia, and the ocular electrophysiology results were consistent with retinitis pigmentosa. Initial laboratory results were as follows: hemoglobin 11.03 g/dL, urea 56.65 mg/dL, creatinine 2.59 mg/dL, estimated glomerular filtration rate 34.14 mL/min/1.73 m². Renal ultrasonography revealed increased parenchymal echogenicity, and abdominal computed tomography revealed small cystic lesions in both kidneys. Kidney biopsy revealed predominantly tubulointerstitial changes (tubular atrophy, basal membrane thickening, and interstitial fibrosis), and immunostaining was negative. Whole-exome sequencing identified homozygous full-gene deletion of IQCB1/NPHP5, confirming the diagnosis of SLS. The patient was managed with conservative and supportive treatments.

Chronic kidney disease in Senior-Løken syndrome is often diagnosed late, leading to a poor clinical outcome. Early diagnosis and timely management of renal complications can prevent the progression to end-stage renal disease.