Adenine Phosphoribosyltransferase or APRT Deficiency: Causes, Symptoms, Treatment, Prognosis
Kidney disorders- There are many medical disorders of the kidney which may give rise to kidney dysfunctions. One such disorder is Adenine Phosphoribosyltransferase/APRT deficiency. In this article, we will study about the various, causes, symptoms, and how to control Adenine Phosphoribosyltransferase/APRT deficiency.
How Is Adenine Phosphoribosyltransferase or APRT Deficiency Defined?
Adenine Phosphoribosyltransferase or APRT deficiency is a rare type of autosomal recessive disorder, which is characterized by formation and excess excretion of 2, 8-dihydroxyadenine from urine resulting in medical conditions like Urolithiasis and Crystalline Nephropathy.
What Causes Adenine Phosphoribosyltransferase or APRT Deficiency?
Adenine Phosphoribosyltransferase or APRT deficiency is a type of autosomal recessive dysfunction which is caused by mutations in APRT gene which encodes the APRT enzyme. There are two types of APRT defined, type I and type II. Type I Adenine Phosphoribosyltransferase is characterized by complete lack of APRT activity. This is found usually in Caucasian population. Type II Adenine Phosphoribosyltransferase or APRT deficiency is characterized by approximately 25% of APRT activity. This is found generally in the Japanese population, but this classification is not clinically significant.
What Are The Symptoms of Adenine Phosphoribosyltransferase or APRT Deficiency?
Clinical symptoms of Adenine Phosphoribosyltransferase or APRT deficiency include usual symptoms that are generally found with Urolithiasis. The stones found are usually radiolucent. The onset of symptoms is usually between infancy and by the time the individual is about aged 40. There is a small population of individuals who remain absolutely asymptomatic. Adenine Phosphoribosyltransferase or APRT deficiency does not only presents itself as Urolithiasis but can also present as Crystalline Nephropathy as a result of precipitation of 2, 8-dihydroxyadenine into the renal parenchyma. This is also called as DHA nephropathy. This occurs usually in people with episodes of urolithiasis with progressive renal dysfunction. It may also present as Acute Renal Failure.
How is Adenine Phosphoribosyltransferase or APRT Deficiency Diagnosed?
Since most of the individuals are not quite aware of Adenine Phosphoribosyltransferase or APRT deficiency, which results in delay between symptom onset and a confirmed diagnosis. Diagnosis is usually based on examining the crystals or stones to look for 2, 8-dihydroxyadenine. In people with DHA nephropathy, renal biopsy can also be done to identify crystals. The crystals and stones need to be completely analyzed using morphologic examination as well as Infrared Spectrometry. A diagnosis of Adenine Phosphoribosyltransferase or APRT deficiency can also be confirmed by analyzing the enzyme activity in erythrocyte lysate.
There is a general confusion between 2, 8-dihydroxyadenine and uric acid stones since they are both radiolucent, but 2, 8-dihydroxyadenine stones generally do not respond to alkaline therapy where as uric acid stone do.
Treatment For Adenine Phosphoribosyltransferase or APRT Deficiency
For Adenine Phosphoribosyltransferase or APRT deficiency, genetic counseling can be done, but is not usually indicated, although since Adenine Phosphoribosyltransferase is an autosomal recessive disorder direct relatives of the affected person need to screened even if they do not have any symptoms of APRT deficiency.
In order to prevent further 2, 8-dihydroxyadenine formation, treatment allopurinol on a daily basis is generally prescribed at 10 mg/kg a day in children and 300 mg a day in adults along with adequate fluid intake and diet consisting of little purine. In instances where there is acute or chronic kidney failure, allopurinol needs to be reduced. People who are not symptomatic can be treated with allopurinol to avoid renal problems.
Prognosis of Adenine Phosphoribosyltransferase or APRT Deficiency
Early diagnosis is imperative and prognosis of Adenine Phosphoribosyltransferase or APRT deficiency is dependent on its progression. It is definitely a treatable dysfunction and allopurinol is quite effective to prevent stones. In case of a deficient renal function, allopurinol therapy helps improving it.