What is the role of lab tests in the workup of Prader-Willi syndrome (PWS)?

Updated: Oct 14, 2020
  • Author: Ann Scheimann, MD, MBA; Chief Editor: Luis O Rohena, MD, MS, FAAP, FACMG  more...
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See the list below:

  • Genetic testing [53, 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, 54, 55, 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.

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