obsolete inborn amino acid transport disorder

Based on the provided context, it appears that there are several inborn errors of amino acid metabolism, but I'll focus on describing an obsolete inborn amino acid transport disorder.

Hartnup Disease

Hartnup disease is a rare, autosomal recessive disorder characterized by defective transport of neutral amino acids across the renal tubular epithelium and intestinal brush border membrane (1). This condition leads to impaired absorption of essential amino acids from the intestine and kidneys, resulting in their excessive excretion in the urine.

The symptoms of Hartnup disease include pellagra-like skin lesions, neurological abnormalities, and developmental delays. The disorder is caused by mutations in the SLC6A19 gene, which encodes a neutral amino acid transporter (2).

Other Obsolete Disorders

Another obsolete disorder mentioned in the context is Iminoglycinuria, a benign condition characterized by impaired reabsorption of glycine, proline, and hydroxyproline in the kidney (14). This disorder is caused by mutations in the SLC3A1 gene.

While these disorders are no longer considered "obsolete" in the sense that they have been well-characterized and their genetic basis understood, they may be less commonly encountered in modern clinical practice due to advances in newborn screening and early detection.

References:

[1] Nippon Rinsho 1992 Jul;50(7):1587-92 [2] Milne MD (1971) [14] Iminoglycinuria is a benign inborn error of amino acid transport characterized by impaired reabsorption of glycine, proline, and hydroxyproline in the kidney.

Based on the provided context, it appears that there are several inborn errors of metabolism related to amino acid transport disorders. Here are some signs and symptoms associated with these conditions:

• Failure to thrive: Infants with a urea cycle disorder or other amino acid metabolism disorders may experience failure to thrive, which can manifest as poor weight gain or loss despite adequate nutrition (7, 9).
• Hepatosplenomegaly: Enlargement of the liver and spleen is a common symptom in various inborn errors of metabolism, including those affecting amino acid transport (6, 8).
• Vomiting: Patients with these disorders may experience vomiting, which can be accompanied by other symptoms such as lethargy, anorexia, and hyperammonemia (1, 7).
• Lethargy and anorexia: Infants with urea cycle disorders or other amino acid metabolism disorders may exhibit signs of lethargy and anorexia, indicating a decline in overall health (1, 7).
• Hypoglycemia: Some inborn errors of metabolism, including those affecting amino acid transport, can lead to hypoglycemia, which is a significant drop in blood sugar levels (4).

It's essential to note that these symptoms can vary depending on the specific disorder and individual case. Additionally, some patients may experience more severe or life-threatening complications if left untreated.

References:

• [1] NA Mew · 2017
• [4] BK Burton · Cited by 475
• [6] Symptoms include failure to thrive, hepatosplenomegaly, and a range of clinical manifestations affecting various organs.
• [7] Jun 22, 2017
• [8] A rare disorder of amino acid absorption and transport characterized by a secondary urea cycle disorder with failure to thrive, hepatosplenomegaly, ...
• [9] Oct 5, 2020

Based on the provided context, it appears that there are several diagnostic tests associated with inborn errors of amino acid metabolism. Here are some relevant tests mentioned:

• Urine organic acid analysis: This test can help identify disorders such as maple syrup urine disease (MSUD) and is useful for diagnosing conditions like glutaric aciduria type 1 [7].
• Plasma amino acid analysis: This test can be used to diagnose conditions such as phenylketonuria and is also helpful in monitoring the nutritional status of individuals with already established diagnosis [7].
• Plasma carnitine levels: Low plasma carnitine levels are associated with fatty acid oxidation disorders, and this test can help identify conditions like carnitine deficiency [9].
• Acylcarnitine profiles: This test can be used to diagnose conditions such as medium-chain acyl-CoA dehydrogenase (MCAD) deficiency [11].

It's worth noting that molecular genetic testing is the primary method of diagnostic confirmation for many inborn errors of amino acid metabolism, including urea cycle disorders (UCDs) [10][12]. This type of testing can help identify specific genetic mutations associated with these conditions.

In addition to these tests, other diagnostic methods may include:

• Enzyme analysis in fibroblasts: This test can be used to diagnose conditions such as ACAT1 deficiency [14].
• Gene sequencing: This test can be used to identify specific genetic mutations associated with inborn errors of amino acid metabolism [10][12].

It's also mentioned that urine organic acids, plasma carnitine levels and acylcarnitine profiles may help identify disorders, but the final diagnosis relies on molecular testing [11].

Based on the provided context, it appears that there are several inborn errors of metabolism (IEMs) related to amino acid transport disorders. However, I couldn't find any specific information on a "obsolete" inborn amino acid transport disorder.

That being said, I can provide some general information on the treatment of IEMs related to amino acid transport disorders.

• Primary treatment for many of these disorders involves dietary restriction of the problematic amino acid and metabolic precursors [4].
• Medication therapy used in IEM often consists of nutritional or herbal supplements or medications that an institution may not routinely carry [10].
• In some cases, treatments may include special diets, medicines, and supplements [9].

It's worth noting that the treatment options for IEMs can vary depending on the specific disorder and its severity. If you could provide more context or clarify which obsolete inborn amino acid transport disorder you are referring to, I may be able to provide more specific information.

Some examples of IEMs related to amino acid transport disorders include:

• Hartnup disease [5], a rare genetic disorder that involves an inborn error of amino acid metabolism.
• Phenylketonuria (PKU) [7], a genetic disorder characterized by an inability to break down the amino acid phenylalanine.

Please let me know if you have any further questions or if there's anything else I can help with.

The differential diagnosis for an obsolete inborn error of amino acid transport disorder, such as defective transport of dibasic cationic amino acids lysine, arginine, and ornithine at the basolateral membrane of epithelial cells in the renal tubules and small intestine [10], would involve considering various conditions that present with similar symptoms.

• Other metabolic disorders: Conditions like urea cycle disorders (UCDs) and maple syrup urine disease (MSUD) can have overlapping symptoms with amino acid transport disorders.
• Genetic disorders: Certain genetic conditions, such as cystic fibrosis, can also present with symptoms related to impaired nutrient absorption.
• Infections: Infections, especially those affecting the gastrointestinal tract, can cause similar symptoms to amino acid transport disorders.
• Cerebrovascular accidents: Seizures and other neurological symptoms can be caused by cerebrovascular accidents, which may be mistaken for an amino acid transport disorder.

It's worth noting that early diagnosis in an index-patient may prevent the birth of other siblings by means of genetic counseling and prenatal diagnosis [11]. Primary aminoacidopathies can be due to genetically determined transport disorders and enzyme deficiencies in amino acid metabolism or degradation [11].

The clinical expression of amino acid metabolism or transport disorders has a great variety, making differential diagnosis challenging. However, considering the common features of these disorders, such as impaired nutrient absorption and metabolic disturbances, can help narrow down the possibilities.

References: [10] [11]