<unk>  phenotype at 15 years of age: Note absence of typical PWS facial features and presence of mild truncal obesity. PWS symptoms can range from poor muscle tone during infancy to behavioral problems in early childhood. Some symptoms usually found in infants, besides poor muscle tone, are a lack of eye coordination, some are born with almond-shaped eyes, and due to poor muscle tone, some may not have a strong sucking reflex. Their cries are weak, and they have difficulty waking up. Another sign of this condition is a thin upper lip. More aspects seen in a clinical overview include hypotonia and abnormal neurologic function, hypogonadism, developmental and cognitive delays, hyperphagia and obesity, short stature, and behavioral and psychiatric disturbances. Holm et al. (1993) describe the following features and signs as indicators of PWS, although not all<unk> be present. In-Utero and birth Childhood Adulthood Physical appearance Neurocognitive Individuals with PWS are at risk of learning and attention difficulties. Curfs and Fryns (1992) conducted research into the varying degrees of learning disability found in PWS. Cassidy found that 40% of individuals with PWS have borderline/low average intelligence, a figure higher than the 32% found in Curfs and Fryns' study. However, both studies suggest that most individuals (50–65%) fall within the mild/borderline/low average intelligence range. Children with PWS show an unusual cognitive profile. They are often strong in visual organization and perception, including reading and vocabulary, but their spoken language (sometimes affected by hypernasality) is generally poorer than their comprehension. A marked skill in completing jigsaw puzzles has been noted, but this may be an effect of increased practice. Auditory information processing and sequential processing are relatively poor, as are arithmetic and writing skills, visual and auditory short-term memory, and auditory attention span. These sometimes improve with age, but deficits in these areas remain throughout adulthood. PWS may be associated with psychosis. Behavioral PWS is frequently associated with a constant insatiable appetite, which persists no matter how much the patient eats, often resulting in morbid obesity. Caregivers need to strictly limit the patients' access to food, usually by installing locks on refrigerators and on all closets and cabinets where food is stored. It is the most common genetic cause of morbid obesity in children. Currently, no consensus exists as to the cause for this symptom, although genetic abnormalities in chromosome 15 disrupt the normal functioning of the hypothalamus. Given that the hypothalamic arcuate nucleus regulates many basic processes, including appetite, a link may well exist. In the hypothalamus of people with PWS, nerve cells that produce oxytocin, a hormone thought to contribute to satiety, have been found to be abnormal. People with PWS have high ghrelin levels, which are thought to directly contribute to the increased appetite, hyperphagia, and obesity seen in this syndrome. Cassidy states the need for a clear delineation of behavioral expectations, the reinforcement of behavioural limits, and the establishment of regular routines. The main mental health difficulties experienced by people with PWS include compulsive behaviour (usually manifested in skin picking) and anxiety. Psychiatric symptoms, for example, hallucinations, paranoia and depression, have been described in some cases and affect about 5–10% of young adults. Patients are also often extremely stubborn and prone to anger. Psychiatric and behavioural problems are the most common cause of hospitalization. Typically, 70–90% of affected individuals develop behavioral patterns in early childhood. Aspects of these patterns can include stubbornness, temper tantrums, controlling and manipulative behavior, difficulty with change in routine, and compulsive-like behaviors. Endocrine Several aspects of PWS support the concept of a growth hormone deficiency. Specifically, individuals with PWS have short stature, are obese with abnormal body composition, have reduced fat-free mass, have reduced lean body mass and total energy expenditure, and have decreased bone density. PWS is characterized by hypogonadism. This is manifested as undescended testes in males and benign premature adrenarche in females. Testes may descend with time or can be managed with surgery or testosterone replacement. Adrenarche may be treated with hormone replacement therapy. Ophthalmologic PWS is commonly associated with development of strabismus. In one study, over 50% of patients had strabismus, mainly esotropia.
Prader–Willi syndrome
Spinal muscular atrophy
Bardet–Biedl syndrome
Myotonic dystrophy
Beckwith–Wiedemann syndrome
Genetics of obesity
Wiedemann–Rautenstrauch syndrome
1p36 deletion syndrome