Loken Senior Syndrome

At a glance

It is an inherited disorder characterized by rapidly progressive renal insufficiency (nephronophthisis) and retinitis pigmentosa. Clinically, it is characterized by renal cysts during infancy or early childhood. Affected individual will potentially experience renal failure and vision loss. Nephronophthisis is associated with anemia, polyuria, polydipsia, and uremia. Other features include mental retardation and arterial hypertension. The degree of retinitis pigmentosa will be an important consideration in the management of the patient at the time of anesthesia. Patients affected might be blind and will require special attention and reassurance.

Synonyms

Familial Juvenile Nephronophthisis with Associated Ocular Anomaly; Hereditary Renal Dysplasia-Blindness; Renal Dysplasia-Retinal Aplasia, Loken-Senior Type; Familial Renal-Retinal Dystrophy; Renal-Retinal Syndrome; Senior-Biochi Syndrome; Senior-Loken Syndrome.

History

It was first described in 1961 by Drs Aagot C. Loken and Boris Senior.

Classification

There are two types of Loken Senior Syndrome based on the age of onset of the symptoms.

• Juvenile Type: The onset of the disease is in infancy or early childhood and is characterized by blindness and renal failure leading to death before the age of 10.

• Adult Type: Presents as a milder course and appears later in life.

Incidence

Incidence of all nephrophthisis disorders is approximately 1:1,000,000 population in the United States and still more in Europe. No racial predilection; both sexes are equally affected.

Genetic inheritance

The inheritance is suspected as an autosomal recessive with variable expression. Gene map locus mostly unknown. Candidate loci are 1p36, 2q12-q13, and 15q.

Pathophysiology

The function of δ₆ integrin is defective. Probably as a compensatory mechanism, there is also an abnormal expression of the δ₅ integrin fibronectin receptor in the tubular basement membrane. This process may lead to destruction of the tubular basement membrane, resulting in gradual loss of kidney function and development of cysts in the renal medulla.

Diagnosis

Renal insufficiency and severe normocytic and normochromic anemia. Serum erythropoietin concentration is lower than in patients with other progressive renal diseases. Laboratory findings indicative of renal failure: metabolic acidosis, hypocalcemia hyperphosphatemia, elevated serum BUN and creatinine concentrations. Imaging studies show the presence of multiple kidney cysts, typically in the medulla and corticomedullary region. Ophthalmoscopy and electroretinography are consistent with tapetoretinal degeneration. Renal biopsy shows typical lesions. The prognosis is poor (death before age 10 years in most patients).

Clinical aspects

There are two types of this disorder. Symptoms varies with the age of onset and include high urine output (patient cannot concentrate the urine), nocturia, headache, anorexia, progressive weakness, and weight loss. This medical condition progresses from chronic renal failure to end-stage renal disease and ...