seroconversion, at time of the most recent anti- GAL IgG test); only 47 of416males tolerized (11%, 95% CI: 8%–15%), compared to 17 of 31 females(55%, 95%CI: 36%–72%). Therewere no statistically significant differencesin endogenous (in vitro) levels of plasma or leukocyte GAL enzymeactivity between patients who had seroconverted and patients who hadnot. However, only a subset of patients who had seroconverted reportedcorresponding plasma or leukocyte GAL enzyme activity data (222 of 416males [53%] and15 of 31 females [48%]). In summary, relatively fewFabryRegistry females developed antibodies against agalsidase beta. Thosefemales who did develop antibodies had much lower peak titer valuesthan males and were likely to tolerize.

doi:10.1016/j.ymgme.2010.11.169

Pulmonary disease and exercise tolerance in boys with Fabrydisease: A pilot study

William Wilcox, Cedars-Sinai Medical Center, Los Angeles, CA, USA

Fabry disease (FD) is a X-linked inborn error of metabolism due todecreased activity of alpha-galactosidase A. Subsequent deposition ofGL-3 causes acroparesthesias, angiokeratomas, strokes, hypertrophiccardiomyopathy, renal failure, hypohidrosis and exercise intolerance.

Enzyme replacement therapy (ERT) reduces GL-3 accumulation,improving many clinical symptoms and stabilizing renal function.While gastrointestinal symptoms, pain, and renal disease begin inchildhood, when to start ERT in a child is controversial.

Pulmonary involvement is an under-recognized component of FD.In our center, the majority of adult FD patients had abnormalpulmonary function tests (PFTs) with reduced FEF25-75 anddecreased V02max on treadmill testing. Furthermore, the diastolicblood pressure declined with increasing exercise, an abnormality thatcorrelated with fatigue in females.

Children with FD often complain of exercise intolerance, but theyhave not been formally evaluated. We hypothesize that exerciseintolerance is common in boys with FD and correlates with abnormaltreadmill testing and PFTs. If this is true, then PFTs and exercisetesting will be important clinical parameters to assess in childhoodand help inform a decision about the timing of ERT initiation.

In this pilot study, we are performing PFTs and treadmill testson 20 FD boys between ages 8 and 18 who have not been treated withERT. To date, 2 boys have been evaluated, both with markedlyabnormal results. Enrollment is ongoing. Interim results will bepresented.

doi:10.1016/j.ymgme.2010.11.170

Abstracts / Molecular Genetics and Metabolism 102 (2011) S3–S47 S47