Browsing Pathways

4-Hydroxybutyric Aciduria/Succinic Semialdehyde Dehydrogenase Deficiency (SSADH; Gamma-hydroxybutyric acidemia) inhibits the formation of succinate from GABA. This deficiency results in urinary excretion of 4-hydroxybutyric acid. In vivo proton MR also indicates elevated GABA levels as compared with an age-matched control. Symptoms include ataxia, chorea or athetosis, motor retardation, seizures, macrocephaly and delayed or abnormal speech development.

Disease Pathway Succinyl CoA: 3-Ketoacid CoA Transferase (SCOT) deficiency is a rare inherited metabolic disorder causing reduction of ketone body utilization. In normal functioning patients, ketone bodies such as Acetoacetate (AcAc) and 3‐hydroxybutyrate (3HB) are metabolized inside the liver from free fatty acids. Next, ketone bodies are transported to extrahepatic tissues via the blood stream. Once in extrahepatic tissues, SCOT converts AcAc to acetoacetyl‐CoA and T2 cleaves acetoacetyl‐CoA into acetyl‐CoA. This process is crucial for producing alternative energy sources to glucose in order to maintain blood glucose levels. Patients with SCOT deficiency have this process disturbed and ketoacidosis which is the acidification of the bloodstream due to excess ketone body accumulation, can occur. Current treatments include avoiding actions that could onset ketoacidosis such as fasting and early infusion of glucose. The severity of SCOT deficiency differs from patient to patient. Some exhibit severe genotypes where ketones are always in abundance in the body, while others could have mild genotypes with no preeminent ketosis however both could exhibit ketoacidotic episodes.

Aromatase deficiency is a rare inborn error of metabolism (IEM) and autosomal recessive disorder of mutations in the CYP19A1 gene. The CYP19A1 gene encodes for the enzyme aromatase. Aromatase converts androgens to estrogens which is vital for bone growth and regulation of blood sugar levels. Symptoms of decrease in estrogen and increase androgens such as testosterone can cause impaired female sexual development, unusual bone growth, insulin resistance, and a variety of other symptoms. It presents with virilization of pregnant mothers during the antenatal period, and virilization of female fetuses at birth. Treatments include lifelong hormone therapy. There have been about 20 reported cases of Aromatase Deficiency worldwide.

17-beta hydroxysteroid dehydrogenase III deficiency, also known as 17-KSR deficiency or male pseudohermaphroditism with gynecomastia (MPH), is as rare inborn error of metabolism (IEM) and autosomal recessive disorder of the androgen and estrogen metabolism pathway. It is caused by a mutation in the HSD17B3 gene, which encodes the enzyme testosterone 17-beta-dehydrogenase 3, which is responsible for catalyzing the reversible formation of androstenedione from testosterone. This leads to an accumulation of androstenedione and dehydroepiandrosterone in the body, as well as a lack of testosterone produced. 17-KSR deficiency is characterized by an absence of testosterone in the testis until puberty, where testosterone is produced outside of the gonads. Symptoms include infertility and external female genitalia until puberty, when secondary male sex characteristics occur, as well as gynecomastia. Due to this, many individuals with this disorder are raised as female despite being genetically male, until puberty. Treatment can include removal of testes before puberty, preventing any masculinization at puberty, as well as surgical treatment of genitalia. However, there is no known treatment for restoring the fertility of affected individuals. It is estimated that 17-KSR deficiency affects 1 in 150,000 individuals in The Netherlands, without much information for the rest of the world.

Hypoacetylaspartia, also known as N-acetylaspartate (NAA) deficiency is an extremely rare autosomal recessive inborn error of metabolism (IEM) caused by a mutation in the NAT8L gene. This gene encodes the N-acetylaspartate synthase protein, which catalyzes the formation of N-acetyl-L-aspartate from L-aspartate and acetyl-CoA, with CoA and a hydrogen ion being byproducts. This reaction occurs as part of the aspartate metabolism pathway. This disorder is characterized by a deficiency of NAA in the brain, as shown by magnetic resonance spectroscopy (MRS). Symptoms of the disorder include microcephaly, developmental delays, ataxia and seizures, which have been shown to worsen the ataxia. So, only one patient has been diagnosed with Hypoacetylaspartia.

Canavan Disease (Canavan-Van Bogaert-Bertrand Disease; Aminoacylase 2 Deficiency; Spongy Degeneration of the Central Nervous System; Aspartoacylase Deficiency; ASP Deficiency; ACY2 Deficiency; ASPA) is a rare autosomal recessive disease caused by a defect in the ASPA gene which codes for aspartoacylase. A deficiency in this enzyme results in accumulation of N-Acetyl-L-aspartic acid in plasma, spinal fluid, and urine. Symptoms, which present at birth, include myclonus, irritability, hypotonia, motor retardation, and poor head control. The neurological complications are due to demyelination of neurons and leukodystrophy. Premature death often results, though lithium citrate can be used as a treatment.

Holocarboxylase synthetase deficiency also called Multiple Carboxylase Deficiency, Neonatal or Early Onset Form, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder of either mutations in the BTD gene or the HLCS gene. The BTD gene encodes for biotinidase and the HLCS gene encodes for holocarboxylase synthetase. This disorder is classified as a multiple carboxylase deficiency, a group of disorders characterized by impaired activity of enzymes dependent on biotin. Symptoms of holocarboxylase synthetase deficiency typically appear within the first few months of life, and include difficulty feeding, breathing problems, a skin rash, hair loss, and lethargy. Treatment using biotin supplements if immediate and lifelong can be effective in preventing many complications and managing the disorder. However, if left untreated the disorder can lead to delayed development, seizures, and coma.

Biotinidase deficiency (Multiple carboxylase deficiency) is an autosomal recessive disease caused by a mutation in the BTD gene which codes for biotinidase. A deficiency in this enzyme results in accumulation of ammonia and ketone bodies in blood; 3-hydroxyisovaleric acid in plasma, spinal fluid, and urine; hydroxypropionic acid, 2-hydroxybutyric acid, 3-Hydroxybutyric acid, and citric acid in spinal fluid; and 3-methylcrotonylglycine, hydroxypropionic acid, and L and D-lactic acid in urine. Symptoms, which can present from birth into adulthood include hypotonia, ketosis, hyperammonemia, motor retardation, coma, and seborrhoic skin rash. Treatment includes biotin.

Hereditary fructose intolerance, also called hereditary fructose-1-phosphate aldolase deficiency or hereditary fructosemia, is rare inborn error of metabolism (IEM) and autosomal recessive disorder of the fructose and mannose degradation pathway. It is caused by a mutation in the ALDOB gene, which encodes fructose-bisphosphatse aldolase B, also known as aldolase B or liver-type aldolase. This enzyme normally cleaves fructose 1,6-bisphosphate into dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate, isomers of one another that are later used in glycolysis. Hereditary fructose intolerance is characterized by an accumulation of fructose-1-phosphate in the liver, as well as a depletion of ATP due to glycolysis having less input than necessary. Symptoms of this disorder include hypoglycemia, abdominal pain and vomiting as well as other symptoms after ingesting fructose. After repeated ingestion of fructose, liver and kidney damage can occur, as well as growth retardation, seizures, and even death. Hereditary fructose intolerance can be treated by eliminating fructose from the diet, and multivitamins can be prescribed to make up for the lack of fruits, a major source of fructose, in the diet. It is estimated that hereditary fructose intolerance affects 1 in between 20,000 and 30,000 individuals.

Fructosuria, full name essential fructosuria, is a condition that presents no symptoms and is benign. Patients with this condition exhibit a mutation in the KHK gene, which leads to fructose metabolism not being completed. This is because of a lack of the enzyme fructokinase, found in the liver. It is identified by the presence of fructose in the urine, which in people without the condition should not be present.