These contain additional material from chromosome 21 and occur in about 2.5% of cases. An isochromosome results when the two long arms of a chromosome separate together rather than the long and short arm separating together during egg or sperm development. Trisomy 21
Trisomy 21 (also known by the karyotype 47,XX,+21 for females and 47,XY,+21 for males) is caused by a failure of the 21st chromosome to separate during egg or sperm development (nondisjunction). As a result, a sperm or egg cell is produced with an extra copy of chromosome 21; this cell thus has 24 chromosomes. When combined with a normal cell from the other parent, the baby has 47 chromosomes, with three copies of chromosome 21. About 88% of cases of trisomy 21 result from nonseparation of the chromosomes in the mother, 8% from nonseparation in the father, and 3% after the egg and sperm have merged. Mosaicism
Mosaicism is diagnosed when there is a mixture of two types of cells: some cells have three copies of chromosome 21 but some cells have the typical two copies of chromosome 21. Mosaicism is the least common form of Down syndrome and accounts for only about 1% of all cases of Down syndrome. Children with mosaic Down syndrome may have the same features as other children with Down syndrome. However, they may have fewer characteristics of the condition due to the presence of some (or many) cells with a typical number of chromosomes.
Amitriptyline is not significantly different from placebo when used for the prevention of migraine in children.Amitriptyline may reduce the frequency and duration of chronic tension headache, but it is associated with worse adverse effects than mirtazapine. Overall, amitriptyline is recommended for tension headache prophylaxis, along with lifestyle advice, which should include avoidance of analgesia and caffeine. Other indications
Amitriptyline is effective for the treatment of irritable bowel syndrome; however, because of its side effects, it should be reserved for select patients for whom other agents do not work. There is insufficient evidence to support its use for abdominal pain in children with functional gastrointestinal disorders.Tricyclic antidepressants decrease the frequency, severity, and duration of cyclic vomiting syndrome episodes. Amitriptyline, as the most commonly used of them, is recommended as a first-line agent for its therapy.Amitriptyline may improve pain and urgency intensity associated with bladder pain syndrome and can be used in the management of this syndrome. Amitriptyline can be used in the treatment of nocturnal enuresis in children. However, its effect is not sustained after the treatment ends. Alarm therapy gives better short- and long-term results.In the US, amitriptyline is commonly used in children with ADHD as an adjunct to stimulant medications without any evidence or guideline supporting this practice. Many physicians in the UK (and the US also) commonly prescribe amitriptyline for insomnia; however, Cochrane reviewers were not able to find any randomized controlled studies that would support or refute this practice.