Summary about Disease
Xanthinuria type II is a rare, inherited metabolic disorder caused by a deficiency of both xanthine dehydrogenase and aldehyde oxidase. This deficiency leads to an abnormal accumulation of xanthine in the blood and urine. Unlike type I, which has only xanthine dehydrogenase deficiency, type II involves an additional enzyme deficiency, potentially leading to a broader range of metabolic effects. Xanthinuria type II can result in the formation of xanthine crystals in the kidneys, which can lead to kidney stones (xanthine urolithiasis) and potentially kidney damage.
Symptoms
Many individuals with xanthinuria type II are asymptomatic. When symptoms occur, they can include:
Kidney stones (xanthine stones)
Hematuria (blood in the urine)
Urinary tract infections
Renal colic (severe pain caused by kidney stones)
Renal failure (in rare, severe cases)
Muscle pain and stiffness (rare)
Arthritis (rare)
Causes
Xanthinuria type II is caused by mutations in the MOCS2 gene. This gene provides instructions for making an enzyme that is essential for the production of molybdopterin, which is required by both xanthine dehydrogenase and aldehyde oxidase to function correctly. Mutations in *MOCS2* lead to a deficiency of molybdopterin cofactor production, which impairs the function of both enzymes, resulting in xanthinuria type II. It is inherited in an autosomal recessive pattern, meaning that an affected individual must inherit two copies of the mutated gene (one from each parent) to develop the disorder.
Medicine Used
There is no specific medication to directly correct the enzyme deficiency in xanthinuria type II. Treatment focuses on managing symptoms and preventing complications. The main strategies include:
Allopurinol: While typically used to treat Type 1 Xanthinuria, it's generally not recommended in Type II. This is because while it decreases xanthine production, it can potentially lead to an increase in hypoxanthine, which, in some cases, can also cause stones.
High fluid intake: Drinking plenty of water (at least 2-3 liters per day) is crucial to dilute the urine and reduce the concentration of xanthine, helping to prevent stone formation.
Dietary modifications: A low-purine diet may be recommended to reduce the amount of xanthine produced in the body. Purines are found in high concentrations in meat, seafood, and some vegetables.
Urine alkalinization: Sodium bicarbonate or potassium citrate may be prescribed to increase the pH of the urine, which can help dissolve xanthine crystals and prevent new stone formation.
Pain relievers: Pain medication may be necessary to manage renal colic caused by kidney stones.
Surgical intervention: In some cases, surgery or other procedures may be necessary to remove large or obstructing kidney stones.
Is Communicable
No, xanthinuria type II is not communicable. It is a genetic disorder caused by a gene mutation and cannot be spread from person to person through any infectious means.
Precautions
Genetic counseling: Families with a history of xanthinuria type II should consider genetic counseling to understand the risk of passing the condition on to their children.
Regular monitoring: Individuals with xanthinuria type II should have regular check-ups with a nephrologist (kidney specialist) to monitor kidney function and detect any complications early.
Adherence to treatment: Following the recommended treatment plan, including adequate fluid intake, dietary modifications, and medication (if prescribed), is crucial to prevent kidney stone formation and other complications.
Informing healthcare providers: Individuals with xanthinuria type II should inform all their healthcare providers about their condition, as it may affect the choice of medications and other medical procedures.
How long does an outbreak last?
Xanthinuria type II isn't characterized by "outbreaks." It's a chronic condition. Symptoms like kidney stones can occur sporadically. Individual episodes of renal colic or urinary tract infections would last based on the specific episode, and would be treated accordingly.
How is it diagnosed?
Diagnosis of xanthinuria type II typically involves:
Urine analysis: Detecting high levels of xanthine in the urine.
Blood tests: Measuring xanthine and uric acid levels in the blood. Uric acid levels are typically low.
Kidney stone analysis: Analyzing the composition of any kidney stones that are passed or removed. Xanthine stones are characteristic of the disorder.
Enzyme assays: Measuring the activity of xanthine dehydrogenase and aldehyde oxidase in liver tissue (rarely done due to invasiveness).
Genetic testing: Identifying mutations in the MOCS2 gene. This is the most definitive diagnostic test.
Timeline of Symptoms
Early childhood: Some individuals may develop symptoms, such as kidney stones, in early childhood.
Adulthood: Other individuals may not develop symptoms until adulthood, or they may remain asymptomatic throughout their lives.
Lifelong: The potential for symptom development exists throughout life. The occurrence of symptoms is dependent on factors like diet, fluid intake, and the severity of the enzyme deficiencies. Regular monitoring is important to detect and manage any complications that may arise.
Important Considerations
Differential diagnosis: It's important to rule out other causes of kidney stones and hyperuricemia (high uric acid levels in the blood) before diagnosing xanthinuria type II.
Asymptomatic individuals: Even if asymptomatic, individuals with xanthinuria type II should be monitored periodically for the development of kidney stones.
Family screening: If an individual is diagnosed with xanthinuria type II, other family members, particularly siblings, should be screened for the condition.
Long-term management: Xanthinuria type II is a lifelong condition that requires ongoing management and monitoring.
Rare Disease: Due to its rarity, it is important to consult with specialists familiar with metabolic disorders and kidney diseases for appropriate diagnosis and management.