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Senior-Loken Syndrome NPHP1 Retinitis — ESENeph MCQ

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HardTubular DisordersSenior-Loken Syndrome NPHP1 RetinitisESENeph

A 18-year-old woman presents with polyuria, polydipsia, short stature, and bilateral medullary cysts on ultrasound. Her eGFR is 40 mL/min/1.73m2. She has no proteinuria. She has a history of retinitis pigmentosa diagnosed at age 10. Genetic testing reveals a homozygous NPHP1 deletion. What is the diagnosis?

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Correct answer: D — Senior-Løken syndrome

The combination of nephronophthisis (medullary cysts, CKD, polyuria/polydipsia from concentrating defect, no proteinuria) with retinitis pigmentosa (retinal dystrophy) defines Senior-Løken syndrome. NPHP1 deletion is the commonest genetic cause of nephronophthisis. Senior-Løken syndrome is a ciliopathy — both renal tubular epithelium and photoreceptors depend on ciliary function. Joubert syndrome would additionally have cerebellar vermis hypoplasia (molar tooth sign on MRI) and developmental delay. Bardet-Biedl syndrome includes obesity, polydactyly, and learning difficulties. ADPKD has large cortical cysts with preserved concentrating ability until late disease.

Reference: Hildebrandt et al 2009 – Ciliopathies; JRCPTB 2022 – Nephrology Curriculum