Morquio B patient/caregiver survey: First insight into the natural course of a rare GLB1 related condition

Morquio B disease (MBD) or Mucopolysaccharidosis type IV B (MPS IV B) is caused by particular GLB1 mutations specifically affecting the affinity of beta-galactosidase to keratan sulphate, resulting in dysostosis multiplex resembling Morquio A (MPS IV A) disease (GALNS deficiency). Additional neuronopathic features of GM1 II/III (juvenile/adult) gangliosidosis have been reported in some patients. Our patient/caregiver online survey was aimed at elucidating the clinical manifestations of this ultra-rare condition. Comparing to previously published data on MPS IV A, the 30 respondents in our MBD group presented with greater growth chart values (weight and height) and with lesser effects of odontoid hypoplasia. The most common concerns are: (1) mobility issues - 84% having difficulty walking; (2) chronic pain - 96%; (3) surgeries - average 3 per person, 80% for hip problems; (4) hip dysplasia, knee/ankle concerns, and scoliosis. Approximately 50% of MBD participants live independently and actively contributing to society. Evidence from our survey results supports the notion that skeletal manifestations in MBD are milder than in the majority of patients with MPS IV A. The data collected will help with the establishment of clinically meaningful outcomes for future therapeutic trials, and with the counseling of newly diagnosed patients about their health expectations.

Retrospective analysis supports algorithm as efficient diagnostic approach to treatable intellectual developmental disabilities

BACKGROUND

Intellectual developmental disorders (IDD(1)), characterized by a significant impairment in cognitive function and behavior, affect 2.5% of the population and are associated with considerable morbidity and healthcare costs. Inborn errors of metabolism (IEM) currently constitute the largest group of genetic defects presenting with IDD, which are amenable to causal therapy. Recently, we created an evidence-based 2-tiered diagnostic protocol (TIDE protocol); the first tier is a 'screening step' applied in all patients, comprising routinely performed, wide available metabolic tests in blood and urine, while second-tier tests are more specific and based on the patient's phenotype. The protocol is supported by an app (www.treatable-ID.org).

OBJECTIVE

To retrospectively examine the cost- and time-effectiveness of the TIDE protocol in patients identified with a treatable IEM at the British Columbia Children's Hospital.

METHODS

We searched the database for all IDD patients diagnosed with a treatable IEM, during the period 2000-2009 in our academic institution. Data regarding the patient's clinical phenotype, IEM, diagnostic tests and interval were collected. Total costs and time intervals associated with all testing and physician consultations actually performed were calculated and compared to the model of the TIDE protocol.

RESULTS

Thirty-one patients (16 males) were diagnosed with treatable IDD during the period 2000-2009. For those identifiable via the 1st tier (n=20), the average cost savings would have been $311.17 CAD, and for those diagnosed via a second-tier test (n=11) $340.14 CAD. Significant diagnostic delay (mean 9 months; range 1-29 months) could have been avoided in 9 patients with first-tier diagnoses, had the TIDE protocol been used. For those with second-tier treatable IDD, diagnoses could have been more rapidly achieved with the use of the Treatable IDD app allowing for specific searches based on signs and symptoms.

CONCLUSION

The TIDE protocol for treatable forms of IDD appears effective reducing diagnostic delay and unnecessary costs. Larger prospective studies, currently underway, are needed to prove that standard screening for treatable conditions in patients with IDD is time- and cost-effective, and most importantly will preserve brain function by timely diagnosis enabling initiation of causal therapy.