obsolete renal aminoaciduria

Obsolete Renal Aminoacidurias: A Historical Perspective

Renal aminoacidurias, also known as inherited kidney disorders characterized by the abnormally elevated levels of amino acids in urine, have been a subject of study for several decades. While many of these conditions are still relevant today, some have been reclassified or considered obsolete due to advances in medical knowledge and understanding.

Types of Obsolete Renal Aminoacidurias

• Cystinuria: This condition was once classified as a distinct type of renal aminoaciduria, but it is now recognized as a specific disorder caused by mutations in the SLC3A1 gene. [3][6]
• Lysinuric Protein Intolerance (LPI): While LPI is still considered a valid medical condition, some earlier classifications and descriptions of this disorder have been superseded by more recent research. [4][7]
• Hartnup Disorder: This condition was once thought to be a distinct type of renal aminoaciduria, but it is now recognized as a specific disorder caused by mutations in the SLC6A19 gene. [5][8]

Characteristics and Symptoms

Obsolete renal aminoacidurias were characterized by the abnormal reabsorption of free amino acids at the proximal renal tubules, leading to elevated levels of these substances in the urine. The symptoms associated with these conditions included:

• Renal dysfunction: Impaired kidney function was a common feature among obsolete renal aminoacidurias.
• Amino aciduria: Elevated levels of amino acids in the urine were a hallmark of these conditions.
• Other systemic effects: Some individuals with obsolete renal aminoacidurias may have experienced other systemic effects, such as growth failure, hypophosphatemic rickets, and porphyria-like symptoms. [12][13]

Current Understanding

While obsolete renal aminoacidurias are no longer considered distinct medical conditions, the underlying genetic mutations that cause these disorders remain an important area of research. Advances in our understanding of these conditions have led to improved diagnostic tools and treatment options for individuals affected by them.

References:

[3] Cystinuria: A specific disorder caused by mutations in the SLC3A1 gene. [4] Lysinuric Protein Intolerance (LPI): A condition characterized by impaired renal reabsorption and intestinal absorption of dibasic amino acids. [5] Hartnup Disorder: A specific disorder caused by mutations in the SLC6A19 gene. [7] Impaired renal reabsorption and intestinal absorption of dibasic amino acids in LPI. [8] Mutations in the SLC6A19 gene cause Hartnup Disorder. [12] Systemic effects associated with obsolete renal aminoacidurias, including growth failure, hypophosphatemic rickets, and porphyria-like symptoms.

Based on the provided context, it appears that renal aminoaciduria is an outdated term for a condition related to abnormal amino acid transport in the kidneys.

Historical Context Renal aminoaciduria was once considered a distinct entity, but it has since been subsumed under more specific conditions. However, we can still glean some information from the context about its historical presentation.

• Glycosuria and Aminoaciduria: According to [9], glycosuria (sugar in the urine) and aminoaciduria (amino acids in the urine) were prominent features of renal aminoaciduria.
• Phosphaturia and Proteinuria: The same study found that phosphaturia (phosphate in the urine) and proteinuria (protein in the urine) occurred in all patients with renal aminoaciduria [9].
• Acidosis and Nitrogen Retention: Acidosis was common, and nitrogen retention was also observed in patients with renal aminoaciduria [9].

Comparison to Modern Conditions While renal aminoaciduria is no longer a distinct diagnosis, its symptoms can be compared to those of modern conditions that involve abnormal amino acid transport.

• Hartnup Disease: Hartnup disease, for example, is a metabolic disorder characterized by abnormal transport of certain amino acids in the kidney and gastrointestinal system [15]. Some signs and symptoms of Hartnup disease include skin photosensitivity, neurologic findings, and renal tubular acidosis.
• Other Aminoacidurias: Other inherited aminoacidurias, such as cystinuria, lysinuric protein intolerance, Hartnup disorder, iminoglycinuria, and dicarboxylic aminoaciduria, also involve abnormal amino acid transport [10, 13, 14].

Conclusion While renal aminoaciduria is an outdated term, its historical presentation can be inferred from the context. The condition was characterized by glycosuria, aminoaciduria, phosphaturia, proteinuria, acidosis, and nitrogen retention. Its symptoms can be compared to those of modern conditions that involve abnormal amino acid transport.

References: [9] M Fulop · 1965 · Cited by 69 [10] Inherited aminoacidurias are caused by defective amino-acid transport through renal (reabsorption) and in many cases also small intestinal epithelia (absorption). [13] In this review, we summarize the latest findings in the clinical and molecular aspects concerning the principal aminoacidurias, cystinuria ... [14] Inherited aminoacidurias are caused by defective amino-acid transport through renal (reabsorption) and in many cases also small intestinal epithelia (absorption). [15] Hartnup disease is a metabolic disorder characterized by abnormal transport of certain amino acids in the kidney and gastrointestinal system.

Diagnostic Tests for Obsolete Renal Aminoaciduria

Renal aminoaciduria, also known as Fanconi syndrome, is a rare disorder characterized by the abnormal reabsorption of amino acids in the proximal renal tubules. While this condition is now considered obsolete due to advances in molecular genetic testing, there are still some diagnostic tests that can be used to confirm its presence.

1. Ammonium Chloride Test

The ammonium chloride test was once used to diagnose distal renal tubular acidosis with failure to acidify the urine to a pH of less than 5.3 (Context #1). However, this test is no longer relevant for diagnosing renal aminoaciduria.

2. Amino Acid Chromatogram

An amino acid chromatogram can be performed in plasma, urine, and cerebrospinal fluid (CSF) to identify the accumulation of amino acids (Context #3). This test may be useful in identifying the presence of aminoacidopathies, such as maple syrup urine disease.

3. 24-Hour Urine Collection

A 24-hour urine collection can be used to confirm the presence of aminoaciduria and potassium wasting in Fanconi syndrome (Context #4).

4. Renal Acidification Studies

Renal acidification studies can be performed to assess the ability of the kidneys to acidify the urine (Context #4). However, these tests are no longer relevant for diagnosing renal aminoaciduria.

5. Laboratory Evaluation

The diagnosis of RTA depends entirely on laboratory evaluation of blood and urine acid-base parameters and electrolyte concentrations (Context #8).

In summary, while there are some diagnostic tests that can be used to confirm the presence of obsolete renal aminoaciduria, these tests are no longer relevant for diagnosing this condition. Molecular genetic testing is now the primary method of diagnostic confirmation.

References:

• Context #1
• Context #3
• Context #4
• Context #8

Treatment Overview

The treatment for obsolete renal aminoaciduria, also known as inherited aminoacidurias, has evolved over the years with advancements in medical science. While specific treatments may vary depending on the underlying cause and severity of the condition, here are some general approaches:

• Conservative therapy: This is often the first line of treatment, which includes high fluid intake to keep the urinary cystine below the solubility threshold (around 1000 μmol/l) [5].
• Medications: Various medications have been used to manage renal aminoaciduria, including:
  • Penicillamine: Although its effectiveness has been questioned in some cases [10], it was once considered a treatment option.
  • Tiopronin: This medication has been shown to be approximately 1.5 times as effective as D-penicillamine in treating cystinuria [11].
  • Alpha-lipoic acid: A new agent that has been explored for its potential benefits in managing cystinuria [13].
• Kidney-replacement therapy: In severe cases, kidney replacement therapy may be necessary to manage the condition.

Important Considerations

It's essential to note that treatment approaches can vary depending on individual circumstances. The effectiveness of certain medications may also depend on factors like patient compliance and the presence of other health conditions.

References

[5] Treatment overall is nonspecific and consists mostly of a high fluid intake to keep the urinary cystine below the solubility threshold of about 1000 μmol l −1 ...

[10] The boy's family opted to discontinue treatment and the amino aciduria improved, but it recurred while he was still off the medication. Penicillamine was ...

[11] Tiopronin should be considered first if conservative therapy fails because it has been shown to be approximately 1.5 times as effective as D-...

[13] In this article, we provide an overview of cystinuria with a special emphasis on medical treatment options including new agents such as alpha-lipoic acid.

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The differential diagnosis of obsolete renal aminoaciduria involves identifying conditions that may present with similar symptoms and characteristics as this condition.

Causes of Obsolete Renal Aminoaciduria

• Primary disorders of amino acid metabolism: These include conditions such as maple syrup urine disease, which can cause aminoaciduria due to the accumulation of toxic metabolites in the body [5].
• Renal tubular transport disorders: These are hereditary conditions that affect the kidneys' ability to reabsorb certain amino acids, leading to their excretion in the urine [3].
• Cystinuria: This is a genetic disorder that affects the kidneys' ability to reabsorb cystine and other dibasic amino acids, leading to their accumulation in the urine [15].

Other Conditions with Similar Symptoms

• Renal tubular acidosis (RTA): RTA is a group of disorders characterized by defective acid-base regulation in the kidneys. While not directly related to aminoaciduria, RTA can present with similar symptoms such as metabolic acidosis and electrolyte imbalances [11].
• Congenital hypothyroidism: This condition can cause failure to thrive and constipation in infants, which may be mistaken for renal aminoaciduria [9].

Key Diagnostic Features

• Urine analysis: Aminoaciduria is characterized by the presence of certain amino acids in the urine. However, this finding may also be present in other conditions such as RTA or cystinuria.
• Blood tests: Blood tests can help identify underlying metabolic disorders that may be contributing to the symptoms.
• Imaging studies: Imaging studies such as ultrasound or CT scans may be necessary to rule out other conditions that may be causing similar symptoms.

References

[3] Mar 18, 2022 — Hereditary tubular transport disorders that lead to abnormal aminoaciduria and glycosuria are uncommon but are of major biologic importance. [5] by MA Edwards · 1988 · Cited by 14 — Amino acid chromatography is used to detect both primary disorders of amino acid meta- bolism (e.g. maple syrup urine disease) and disorders of renal tubular ... [9] by JCM Chan · 2001 · Cited by 14 — The differential diagnosis of fail- ure to thrive and constipation in in- fancy must include congenital hypo- thyroidism (Table 3). Results of thyroid ... [11] by SK Haque · 2012 · Cited by 10 — Urine composition is important for the diagnosis of RTA. Patients with normal renal function and intact urinary acidification mechanisms who are exposed to metabolic acidosis will usually produce a urine pH ... [15] Inherited aminoacidurias are caused by defective amino-acid transport through renal (reabsorption) and in many cases also small intestinal epithelia (absorption). Recently, many of the genes causing this abnormal transport have been molecularly identified.