Specimen:

Urine

Collection Medium:

Minimum:

Preferred minimum: 4.5 mL random urine, first-morning void
Pediatric minimum: 3 mL random urine, first-morning void

Delivery Instructions:

Deliver to laboratory immediately after collection.

Analytic Time:

2 weeks

Reference Range:

     Age                  PYR              DPYR        Ratio DPYR/PYR
 0-11 months        Not applicable    Not applicable      0.13-0.20
 1-3 years          Not applicable    Not applicable      0.18-0.24
 4-9 years          Not applicable    Not applicable      0.19-0.25
10-14 years         Not applicable    Not applicable      0.17-0.27
15-19 years         Not applicable    Not applicable      0.20-0.26
20 years and older  Not applicable    Not applicable      0.23-0.29

Test
Limitations:

Ehlers-Danlos Syndrome (EDS) describes a heterogeneous group of 
connective tissue disorders. EDS VI, also known as the kyphoscoliotic 
type, is characterized by hyperextensible skin, joint laxity, 
progressive scoliosis, severe muscle hypotonia at birth, and ocular 
fragility. It is caused by a deficiency of the enzyme lysyl 
hydroxylase. Lysyl hydroxylase is encoded by a gene located on 
chromosome 1p36.3-p36.2 known as procollagen-lysine, 2-oxoglutarate 
5-dioxygenase 1 (PLOD1). This enzyme is essential for the hydroxylation 
of lysine residues on collagen. The derived hydroxylysine residues are 
the precursors of the most stable crosslinks of collagen, pyridinoline, 
and deoxypyridinoline.

The incidence of EDS VI has been estimated at 1 in 100,000 with a 
carrier frequency of 1 in 150. It is inherited in an autosomal 
recessive manner. Although 20 different mutations have been detected in 
the PLOD1 gene, mutation analysis is only being performed on a research 
basis. The diagnosis of EDS VI is performed using HPLC to determine the 
ratio of deoxypyridinoline to pyridinoline in urine. A markedly 
elevated ratio is indicative of the disease. The diagnosis can be 
confirmed by enzyme assay in cultured dermal fibroblasts.

Affected fetuses are at risk for premature rupture of membranes and 30 
percent have clubfoot. Infants usually present with generalized joint 
laxity and muscle hypotonia. Gross milestones, such as walking, may be 
delayed. Thoracic scoliosis is common in childhood and often progresses 
into the moderate to severe range. All affected individuals have 
hyperelastic skin, 60 percent have abnormally thin wide scarring, and 
50 percent experience severe bruising. Most affected individuals have 
high myopia and microcornea, while a minority have ocular fragility, 
glaucoma, or retinal detachment. Frequent joint dislocations can also 
pose a serious problem. Adults with severe kyphoscoliosis may develop 
frequent pneumonia and restrictive lung disease. Affected individuals 
are at increased risk for aortic dilation/dissection, as well as 
rupture of medium-sized arteries.

There are no genotypic/phenotypic correlations that have been 
determined in the few affected individuals whose mutations have been 
determined. Two pathological variants have been observed in more than 
one affected family (gene duplication of 7 exons and Y511X). The most 
sensitive and specific manner to establish a diagnosis of EDS VI 
remains through biochemical testing.

Affected individuals with kyphoscoliosis should be referred for regular 
follow-up with an orthopedic surgeon. Older children, adolescents, and 
adults can benefit from a physical therapy regimen to strengthen large 
muscle groups, particularly the shoulder girdle. They should undergo 
routine screening for inguinal hernia.

Routine ophthalmologic examination may be useful for detection and 
management of myopia and glaucoma. Referral to a cardiologist for an 
echocardiogram for aortic root measurement is recommended every five 
years, even if the initial examination is normal. Antimicrobial 
prophylaxis for individuals with mitral valve prolapse and aggressive 
blood pressure control is critical. Affected individuals may also 
benefit from vitamin C (0.5-10 g per day) to improve muscular strength 
and wound healing.

This test should be offered to individuals with clinical symptoms 
suggesting EDS VI, such as hyperextensible skin, joint hypermobility, 
kyphoscoliosis, easy bruisability, or corneal fragility. All siblings 
of individuals deemed affected should also be tested, since they are at 
25 percent risk for the same disease. Carrier testing cannot be 
performed biochemically or by enzyme assay and is not currently 
clinically available through PLOD1 mutation analysis. Prenatal 
diagnosis is only available through laboratories that perform custom 
DNA analysis for couples who have had a previous affected child with 
identified mutations. Genetic counseling should be offered to all 
affected individuals and their parents.

The HPLC analysis allows the simultaneous quantitation of pyridinoline 
and deoxypyridinoline. In patients with EDS VI, the excretion of 
deoxypyridinoline is markedly increased. As a result, the 
deoxypyridinoline/pyridinoline ratio is also markedly increased (from 
0.2 in normal controls to 4-6 in patients with EDS VI) and allows the 
diagnosis.

Methodology:

High Performance Liquid Chromatography (HPLC)

CPT Code:

82492

See Additional Information:
Specimens Requiring Immediate Delivery