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Hypophosphatemic Rickets, X-Linked

Clinical System Name

Miscellaneous Test


PHEX gene
Vitamin D Resistant Rickets
X-linked Hypophosphatemia


Inherited rickets is often associated with growth retardation, bowing of the lower extremities, and poor dental development. X-linked dominant hypophosphatemic rickets, due to mutations in the PHEX gene, is the most common inherited form of the disorder.

Sample Requirements

Specimen: Whole Blood

Container(s): Lavender Top/EDTA, Yellow/ACD

Preferred Vol: 5 mL

Minimum Vol: 2 mL


Specimen: DNA

Container(s): Sterile plastic tube

Preferred Vol:  5,000 ng (5 µg) at concentration of 50 ng/µL

Minimum Vol:

Processing Instructions

Reject due to: Buccal swabs are not acceptable for this test.

Spin: N

Aliquot: N

Temp: 2-8 C

Storage location: Refrigerate whole blood in CPA refrigerator Sendouts rack. Store labels and a copy of the requisition in the clear plastic box on front of the CPA fridge.


Off-site collection: Send whole blood refrigerated.


Specimen Type Temperature Time
Whole blood Room temp 3 d
Whole blood Refrigerated 7 d
Whole blood Frozen N
Extracted DNA Room temp 3-4 d
Extracted DNA Refrigerated 1 y
Extracted DNA Frozen Indefinitely



N 7-8 w


Performing Laboratory



Department:  GeneDx, 207 Perry Parkway, Gaithersburg, MD 20877

Phone Number: (301) 519-2100

Reference Range

Interpretive report is provided.


Method: the 22 coding exons and splice junctions of the PHEX gene are screened by bi-directional sequence analysis. In females, where sequencing fails to identify a pathogenic mutation, targeted array CGH analysis with exon-level resolution (ExonArrayDx) is performed concurrently to evaluate for a deletion or duplication of one or
more exons of this gene.

Analytical Volume:


CPT Codes

Test code 1861 (Males):  81406


Test code 1861E (Females): 81406 and 81479


(Updated  1/12/2015 by dstern)

Special Instructions

Links to:




Send Out Instructions

Reference Test Name: X-linked Dominant Hypophosphatemia (PHEX)
Reference Test Number: 1861 (Males)/ 1861E (Females)
Instructions: GeneDx accepts Saturday delivery. Whole blood specimens may be stored refrigerated for up to 7 days prior to shipping. Ship whole blood overnight via FedEx, ambient temperature.