Prader-Willi Syndrome Workup

Updated: Aug 27, 2021
  • Author: Ann Scheimann, MD, MBA; Chief Editor: Luis O Rohena, MD, PhD, FAAP, FACMG  more...
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Laboratory Studies

See the list below:

  • Genetic testing [54, 6]

    • Genetic testing for Prader-Willi syndrome (PWS) includes chromosomal or microarray analysis and assessment for methylation patterns in the Prader-Willi syndrome region.

    • Methylation patterns can be determined with Southern blot hybridization or polymerase chain reaction (PCR) using DNA primers that can detect methylated cytosine.

    • Analysis for underlying uniparental disomy requires samples from both parents and the child with Prader-Willi syndrome.

    • Fluorescent in situ hybridization (FISH) can be used to confirm prenatal diagnosis when a deletion in the 15q region is suspected after chorionic villus sampling or amniocentesis.

    • In a patient with an imprinting center mutation, test both biological parents for the presence of asymptomatic mutations in the imprinting center; such mutations indicate a higher risk for recurrence.

  • Hypogonadism [42, 6]

    • Most patients with Prader-Willi syndrome have hypothalamic dysfunction that manifests as short stature, central obesity, hypogonadism, and osteoporosis.

    • Fasting measurements of serum insulinlike growth factor-1 (IGF-1) and insulinlike growth factor binding protein-3 (IGFBP-3) levels are good screening measurements for underlying growth hormone deficiency.

    • Refer patients with diminished growth velocity and abnormal levels of IGF-1 and IGFBP-3 to a pediatric endocrinologist for provocative growth hormone stimulation testing.

    • Assess thyroid and adrenal status in patients when clinically warranted.

    • Hypopituitarism has been reported in some patients with Prader-Willi syndrome.

  • Obesity [42, 55, 56, 6]

    • Measure glycosylated hemoglobin in patients with Prader-Willi syndrome who are obese to assess for the development of type 2 diabetes mellitus as clinically warranted, especially if the patient is taking growth hormone supplementation.

    • Evaluate patients with Prader-Willi syndrome for biochemical evidence of pickwickian syndrome (eg, hypercarbia, polycythemia) as clinically warranted.

    • If symptoms suggest sleep apnea or narcolepsy, perform a sleep study with multiple sleep latency testing.


Imaging Studies

See the list below:

  • Individuals with Prader-Willi syndrome are at risk for pathologic fractures secondary to underlying osteoporosis. A high pain tolerance may allow for minimal symptoms of discomfort with obvious deformity. Patients with Prader-Willi syndrome may require the following imaging studies: [6]

    • MRI of the head (to evaluate for hypopituitarism)

    • Serial dual energy x-ray absorptiometry (DEXA) scanning (for detection and monitoring of osteoporosis) [7]

    • Scoliosis films

      Severe typical scoliosis. Severe typical scoliosis.
    • Chest radiography (if cor pulmonale is suspected)

    • Other imaging modalities as clinically dictated (eg, extremity film for limp evaluation, hip films to screen for hip dysplasia [8] )

  • In patients who suddenly develop abdominal distention, abdominal pain, or a decrease in appetite, imaging including plain abdominal radiography, abdominal ultrasonography, or CT scanning and gastrointestinal series may be warranted to screen for possible conditions such as acute gastric dilation, cholelithiasis, or pancreatitis.



See the list below:

  • Assess the growth hormone axis and adrenal axis under the supervision of an endocrinologist if clinically warranted. [42]