However, the evidence in favour of selective tryptophan restriction remains insufficient and the consensus is evolving towards the restriction of lysine only. In the Amish community, where GA1 is overrepresented, patients with GA1 typically do not receive tryptophan-free formulas, either as the sole source of amino acids or as a supplement to protein restriction. Enhancement of precursor anabolic pathways
Lysine and hydroxylysine anabolic pathway enhancement
A possible way to prevent the build-up of metabolites is to limit lysine and hydroxylysine degradation, as lysine is one of the most abundant amino acids and tryptophan is one of the least abundant amino acids. Interaction of GCDH deficiency with vitamin C levels
Humans lack the enzyme L-gulonolactone oxidase, which is necessary for the synthesis of ascorbic acid (vitamin C), leaving them dependent on dietary sources of this vitamin. Vitamin C is a necessary cofactor for the utilization of lysine in collagen synthesis. Collagen, the most abundant protein in the human body, requires great amounts of lysine, the most abundant amino acid in proteins. Ascorbic acid, the main hydroxyl radical quencher, works as the cofactor providing the hydroxyl radical required for collagen cross-linking; lysine thus becomes hydroxylysine. GA1 worsens during stresses and catabolic episodes, such as fasts and infections. Endogenous catabolism of proteins could be an important route for glutaric acid production. It follows that collagen breakdown (and protein breakdown in general) should be prevented by all possible means. Ascorbic acid is used to prevent multiple organ failure and to lessen mortality and morbidity in intensive care units.
Hallermann–Streiff syndrome is a congenital disorder that affects growth, cranial development, hair-growth, and dental development. There are fewer than 200 people with the syndrome worldwide. One notable organization that is supporting people with Hallermann–Streiff syndrome is the Germany-based "Schattenkinder e.V". Presentation
Patients with this syndrome are shorter than the average person and may not develop hair in many places, including in the facial, leg and pubic areas. Patients also have eye problems including reduced eye size, bilateral cataracts and glaucoma. The syndrome can be associated with sleep apnea. The physical characteristics of the syndrome can result in difficult intubation by medical professionals. Intelligence is usually normal. Cause
The genetic cause of Hallermann–Streiff syndrome has not been conclusively determined. It is most likely due to a de novo mutation, and it may be associated with the GJA1 gene. Diagnosis
Diagnosis is based on the physical characteristics and symptoms. There is no established clinical genetic testing for Hallermann–Streiff syndrome, however some laboratories offer research genetic testing for the condition. Treatment
There is no cure for Hallermann–Streiff syndrome. Treatments center around the particular symptoms in each individual. Early measures are based around ensuring proper breathing and intake of nutrients and may include a tracheostomy. Early surgery for cataracts may be recommended, however some studies have suggested that spontaneous resolution of cataracts occurs in up to 50% of untreated patients.