XLMR with Growth Hormone Deficiency: SOX3 Gene Sequencing

Duplicationsof and in the SOX3 gene (Xq26.3) havebeen associated with X-linked recessive mental retardation with growth hormonedeficiency. Mental retardation is mild to moderate and growth hormone levelscan vary between affected individuals even within families. Some affected maleshave died during the first day of life and exhibited postmortem findings ofhypoadrenalism, presumably due to hypopituitarism. Others have variablecombinations of hypothyroidism, delayed pubertal development, and short staturedue to growth hormone deficiency. All surviving affected individuals exhibitedmild to moderate mental retardation. Behavior in affected individuals has beenconsidered infantile.

Variablecraniofacial dysmorphism has also been reported, including hypertelorism,epicanthus, synophrys, broad nasal bridge, high-arched palate, long philtrum, cuphelices, and coarse facies. In one study, male patients continued to grow untilwell into their twenties and reached a height ranging from 135 to 159 cm. BrainMRI in some affected males showed anterior pituitary hypoplasia, ectopicposterior pituitary, and absent infundibulum.

For patients with suspected XLMR with growth hormone deficiency, 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.

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This test is indicated for:

• Confirmation of a clinical/biochemical diagnosis of XLMR with growth hormone deficiency
• Carrier testing in adult females with a family history of XLMR with growth hormone deficiency

PCR amplification of 1 exon contained in the SOX3 gene is performed on the patient's genomic DNA. Direct sequencing of amplification products is performed in both forward and reverse directions, using automated fluorescence dideoxy sequencing methods. The patient's gene sequences are then compared to a normal reference sequence. Sequence variations are classified as mutations, benign variants unrelated to disease, or variations of unknown clinical significance. Variants of unknown clinical significance may require further studies of the patient and/or family members. This assay does not interrogate the promoter region, deep intronic regions, or other regulatory elements, and does not detect large deletions.

• Deletion/duplication analysis of the SOX3 gene by CGH array is available for those individuals in whom sequence analysis is negative (YV).
• X-Linked Intellectual Disability panels are available for 30, 60, and 90+ genes.
• 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.

Requisition Forms

• Comprehensive Molecular Test Requisition Form
• Autism/Intellectual Disability/Developmental Delays Test Requisition Form

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