The Senior-Loken syndrome is a very rare autosomal recessive that is characterized by eye and kidney abnormalities. Additional symptoms are also possible with this birth defect. The condition is progressive but with fast, multidisciplinary treatment, mortality is reduced. The syndrome was first described in 1961 by Loken and colleagues.
Synonyms Senior Løken Syndrome
The Senior Løken syndrome is also known by these synonyms:
- Juvenile Nephronophthisis with Leber Amaurosis
- Loken Senior Syndrome
- Renal retinal syndrome
- Renal dysplasia and retinal aplasia
- Renal dysplasia-Blindness, Hereditary
- Renal Retina syndrome
- Renal Retina Dysplasia
- Senior Loken syndrome
The Senior Løken syndrome is a rare birth defect, with an estimated prevalence of around 1 in 1 million people worldwide. Several hundred patients have been reported in the medical literature. The Arab population in particular has been described in the literature, although the condition is worldwide. The gender preference of the syndrome has not been found in the literature.
Causes and heredity Senior Løken syndrome
Mutations in one of at least seven genes cause the Senior Løken syndrome (PHP1, INVS, NPHP3, NPHP4, IQCB1, CEP290, SDCCAG8). In some patients, gene mutations cannot be diagnosed and no family history is known. With them, the de novo disorder arises (spontaneously). The inheritance of this condition is autosomal recessive. The parents of a patient with an autosomal recessive disorder each carry one copy of the mutated gene, but usually do not show any symptoms of the disorder themselves.
Symptoms: Kidney and eye abnormalities
The patient has two primary symptoms, namely the kidney disease "nephronophthisis" and the eye disorder "Leber Congenital Amaurosis". The severity and extent of the symptoms vary per patient. Even members of the same family sometimes present themselves with a very different course of the disease. The symptoms often present themselves during the first year of life.
Liquid filled cysts develop in the kidneys of a patient (abnormally shaped body cavities) (nephronophthisis). This starts in childhood. In some families this process is very slow. polyuria (large amounts of urination), polydipsia (very thirsty), asthenia (weakness), and fatigue are some characteristic symptoms of kidney problems. Nephronophthisis leads to a life-threatening stage of renal failure (impaired or absent kidney function) during childhood or adolescence. In this situation, the kidneys are no longer able to filter liquids and waste from the body.
In the infancy or childhood, the retina in the eyes is affected by Leber Congenital Amaurosis (LCA). The retina is located at the back of the eye and is responsible for light and color perception. As a result, the patient experiences vision problems. He is hypersensitive to light (photophobia), has involuntary eye movements (nystagmus) that come to light in the first two months of life, and is extremely distant (hypermetropia). In some situations, the retinal progressive atrophy is similar to the retinitis pigmentosa eye disorder.
Additional symptoms include abnormal formation of connective tissue in the liver (liver fibrosis), coordination disorders, diabetes insipidus (disorder with symptoms of much thirst, frequent urination and large amounts of urination), hearing loss and skeletal abnormalities.
Diagnosis and investigations
A doctor performs a thorough kidney examination in which he tests kidney function, performs a urine test and performs an ultrasound scan of the abdomen. In addition, the eye doctor performs an extensive eye examination via fundoscopy. He also measures the visual acuity, looks at refractive defects, determines the color vision and tests the eye movement. An electroretinogram is recommended. The liver also assesses the doctor to rule out liver fibrosis (liver function and ultrasound of the abdomen). A neurological examination is usually performed on babies. The final diagnosis is done through a genetic test.
The disease cannot be cured, but multidisciplinary treatment is possible. A (pediatric) nephrologist and eye doctor follow the patient. The doctors try to prevent complications and to delay the progression of the disease. In the final phase of the kidney disease, the patient needs dialysis or a kidney transplant. The deterioration of vision cannot be prevented. The patient also benefits from a number of aids for the blind and partially sighted. A blind association and aids supplier provide advice on this.
The patient often dies from kidney failure if treatment is not started in time. The patient usually loses sight at a later age. Further information about the prognosis of this syndrome is missing.