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The disorder results in accumulation of the insoluble purine 2,8-dihydroxyadenine.
It can result in nephrolithiasis (kidney stones), acute renal failure and permanent kidney damage.
More than 300 individuals with this disease have been reported world-wide but it is not known how common this medical problem truly is. Patients with the disease deficiency lack the enzyme adenine phosphoribosyltransferase and therefore have difficulties breaking down dietary substances called purines, resulting in accumulation of a compound called 2,8-dihydroxyadenine (2,8-DHA) that is excreted by the kidneys. Up to 70% of affected patients, have red hair or relatives with this hair color.
Adenine phosphoribosyltransferase deficiency (also called APRT deficiency or 2,8 dihydroxyadenine urolithiasis) is an autosomal recessive metabolic disorder associated with a mutation in the enzyme adenine phosphoribosyltransferase.
Initial treatment is with adequate hydration, alkalization of the urine with citrate supplementation or acetazolamide, and dietary modification to reduce salt and protein intake (especially methionine). If this fails then patients are usually started on chelation therapy with an agent such as penicillamine. Tiopronin is another agent.
Once renal stones have formed, however, the first-line treatment is ESWL (Extracorporeal shock wave lithotripsy). If ESWL do not work efficiently surgery can be necessary. Both endoscopic surgery and conventional open-abdominal surgery have proven to be effective treatment modalities for patients with more advanced disease. Adequate hydration is the foremost aim of treatment to prevent cysteine stones. The goal is to increase the urine volume because the concentration of cystine in the urine is reduced which prevents cystine from precipitating from the urine and forming stones. People with cystine stones should consume 5 to 7 liters a day. The rationale behind alkalizing the urine is that cystine tends to stay in solution and causes no harm. In order to alkalize the urine, sodium biocarbonate has been used. One must be careful in alkalizing their urine because it could lead to other forms of stones in process of preventing cystine stones. Penicillamine is a drug that acts to form a complex with cystine that is 50 times more soluble than cystine itself. Percutaneous nephrolithotripsy (PNL) is performed via a port created by puncturing the kidney through the skin and enlarging the access port to 1 cm in diameter. Most of the time, cystine stones are too dense to be broken up by shock (ESWL) so PNL is needed.
Videos of surgery are available on various websites that show stone removal by percutaneous nephrolithotomy.
In February 2017, an article was published in Nature Medicine entitled 'Alpha lipoic acid treatment prevents cystine urolithiasis in a mouse model of cystinuria', suggesting that a high dose of the readily available antioxidant, alpha-lipoic acid at 2,700 mg/67 kg body weight daily reduced the incidence of stones. The effects were dose dependent. The results are unprecedented for cystinuria. A clinical trial is underway based on this mouse model.
Cystinuria is an inherited autosomal recessive disease that is characterized by high concentrations of the amino acid cystine in the urine, leading to the formation of cystine stones in the kidneys, ureter, and bladder. It is a type of aminoaciduria.
Specific therapy should be tailored to the type of stones involved. Diet can have a profound influence on the development of kidney stones. Preventive strategies include some combination of dietary modifications and medications with the goal of reducing the excretory load of calculogenic compounds on the kidneys. Current dietary recommendations to minimize the formation of kidney stones include:
- Increasing total fluid intake to more than two liters per day of urine output.
- Increasing citric acid intake; lemon/lime juice is the richest natural source.
- Moderate calcium intake
- Limiting sodium intake
- Avoidance of large doses of supplemental vitamin C
- Limiting animal protein intake to no more than two meals daily (an association between animal protein consumption and recurrence of kidney stones has been shown in men).
- Limiting consumption of cola soft drinks, which contain phosphoric acid, to less than one liter of soft drink per week.
Maintenance of dilute urine by means of vigorous fluid therapy is beneficial in all forms of nephrolithiasis, so increasing urine volume is a key principle for the prevention of kidney stones. Fluid intake should be sufficient to maintain a urine output of at least per day. A high fluid intake has been associated with a 40% reduction in recurrence risk. The quality of the evidence for this, however, is not very good.
Calcium binds with available oxalate in the gastrointestinal tract, thereby preventing its absorption into the bloodstream, and reducing oxalate absorption decreases kidney stone risk in susceptible people. Because of this, some nephrologists and urologists recommend chewing calcium tablets during meals containing oxalate foods. Calcium citrate supplements can be taken with meals if dietary calcium cannot be increased by other means. The preferred calcium supplement for people at risk of stone formation is calcium citrate because it helps to increase urinary citrate excretion.
Aside from vigorous oral hydration and consumption of more dietary calcium, other prevention strategies include avoidance of large doses of supplemental and restriction of oxalate-rich foods such as leaf vegetables, rhubarb, soy products and chocolate. However, no randomized, controlled trial of oxalate restriction has yet been performed to test the hypothesis that oxalate restriction reduces the incidence of stone formation. Some evidence indicates magnesium intake decreases the risk of symptomatic nephrolithiasis.
Preventative measures depend on the type of stones. In those with calcium stones, drinking lots of fluids, thiazide diuretics and citrate are effective as is allopurinol in those with high uric acid levels in the blood or urine.
Treatment, depending on cause, may require prompt drainage of the bladder via catheterization, medical instrumentation, surgery (e.g., endoscopy, lithotripsy), hormonal therapy, or a combination of these modalities.
Treatment of the obstruction at the level of the ureter:
Modification of predisposing factors can sometimes slow or reverse stone formation. Treatment varies by stone type, but, in general:
- Medication
- Surgery (lithotomy)
- Antibiotics and/or surgery for infections
- Medication
- Extracorporeal shock wave lithotripsy (ESWL) for removal of calculi
Definitive causes of ureterocele have not been found. While the abnormal growth occurs within the uterus, it has not been substantiated that genetics are to blame.
Stones can cause disease by several mechanisms:
- Irritation of nearby tissues, causing pain, swelling, and inflammation
- Obstruction of an opening or duct, interfering with normal flow and disrupting the function of the organ in question
- Predisposition to infection (often due to disruption of normal flow)
A number of important medical conditions are caused by stones:
- Nephrolithiasis (kidney stones)
- Can cause hydronephrosis (swollen kidneys) and renal failure
- Can predispose to pyelonephritis (kidney infections)
- Can progress to urolithiasis
- Urolithiasis (urinary bladder stones)
- Can progress to bladder outlet obstruction
- Cholelithiasis (gallstones)
- Can predispose to cholecystitis (gall bladder infections) and ascending cholangitis (biliary tree infection)
- Can progress to choledocholithiasis (gallstones in the bile duct) and gallstone pancreatitis (inflammation of the pancreas)
- Gastric calculi can cause colic, obstruction, torsion, and necrosis.
Many other complications arise from ureteroceles. Redundant collection systems are usually smaller in diameter than single, and predispose the patient to impassable kidney stones. The effective "bladder within a bladder" compounds this problem by increasing the collision of uric acid particles, the process by which uric acid stones are formed. Ureterocele is also associated with poor kidney function. It can cause frequent blockage of the ureter leading to serious kidney damage. In other cases, a small, upper portion of the kidney is congenitally non-functional. Though often benign, this problem can necessitate the removal of non-functioning parts.
Obstructive uropathy is a structural or functional hindrance of normal urine flow, sometimes leading to renal dysfunction (obstructive nephropathy).
It is a very broad term, and does not imply a location or cause.
The disease is chronic and often progresses slowly. Prognosis is generally poor when associated with glaucoma [1,2].
Penetrating karatoplasty and endothelial keratoplasty can be used as treatments for severe cases of ICE [2,8]. Because glaucoma and elevated intraocular pressure are often present in ICE patients, long term follow up may be needed to ensure adequate intraocular pressures are maintained [2,7]