Mutationsin the PQBP1 gene (Xp11.23) causeX-linked recessive mental retardation that is often syndromic but can benonsyndromic. PQBP1 mutations havebeen associated with Renpenning syndrome, Sutherland-Hann syndrome, cerebropalatocardiac(Hamel) syndrome, and Golabi-Ito-Hall syndrome. Common features of X-linkedmental retardation caused by PQBP1 mutation seem to be mental retardation, microcephaly, and short stature. Considerablephenotypic variability is observed between families with different mutationsand even between families with the same mutation.
Inaddition to mental retardation, microcephaly, and short stature, other reportedfeatures include small testes, ocular colobomas, cardiac malformations, cleftpalate, spastic diplegia, and anal anomalies. Facial characteristics includenarrow and tall craniofacies with upslanting palpebral fissures, abnormal nasalconfiguration, cupped ears, and short philtrum. The nose may appear long orbulbous, with overhanging columella.
Historically, Renpenning syndromehas been associated with mental retardation with short stature, moderatemicrocephaly, but no remarkable facies and no other neurologic abnormalities.Sutherland-Haan syndrome has been associated with mental retardation, shortstature, microcephaly, brachycephaly, spastic diplegia, small testes, andpossibly intrauterine growth retardation. Cerebropalatocardiac (Hamel) syndromehas been associated with severe mental retardation with congenital heart defects,microcephaly, spasticity, short stature, cleft or highly arched palate, andother craniofacial abnormalities. Golabi-Ito-Hall syndrome has been associatedwith mental retardation, microcephaly, postnatal growth deficiency, and otheranomalies, including atrial septal defect.
For patients with suspected Renpenning syndrome, sequence analysis is recommended as the first step in mutation identification. For patients in whom mutations are not identified by full gene sequencing, deletion/duplication analysis is appropriate.
Click here for the OMIM summary on this condition.
This test is indicated for:
- Confirmation of a clinical/biochemical diagnosis of Renpenning syndrome
- Carrier testing in adult females with a family history of Renpenning syndrome
Clinical Sensitivity: Unknown. Mutations in the promoter region, some mutations in the introns and other regulatory element mutations cannot be detected by this analysis. Large deletions will not be detected by this analysis. Results of molecular analysis should be interpreted in the context of the patient's biochemical phenotype.
Analytical Sensitivity: ~99%
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
Infants and Young Children (<2 years of age): 2-3 ml
Children > 2 years of age to 10 years old: 3-5 ml
Older Children & Adults: 5-10 ml
Autopsy: 2-3 ml unclotted cord or cardiac blood
Orangene™ Saliva Collection Kit used according to manufacturer instructions. Please contact EGL for a Saliva Collection Kit for patients that cannot provide a blood sample.
Submit copies of diagnostic biochemical test results with the sample, if appropriate. Contact the laboratory if further information is needed.
Sequence analysis is required before deletion/duplication analysis by targeted CGH array. If sequencing is performed outside of EGL Genetics, please submit a copy of the sequencing report with the test requisition.
- Deletion/duplication analysis of the PQBP1 gene by CGH array is available for those individuals in whom sequence analysis is negative (YQ).
- A CGH array-based test for deletion/duplication analysis of 64 different X-linked intellectual disability genes is available (OL).
- Custom diagnostic mutation analysis (KM) is available to family members if mutations are identified by targeted mutation testing or sequencing analysis.
- Prenatal testing is available to adult females who are confirmed carriers of mutations. Please contact the laboratory genetic counselor to discuss appropriate testing prior to collecting a prenatal specimen.