MLD is an ultra-rare neurodegenerative disease leading to progressive motor and cognitive decline. At present, US patients with early-onset MLD (<7 years of age at onset) have no disease modifying treatment options and have very poor survival outcomes, often reaching a decerebrated state or death before adolescence. Due to the debilitating nature of early-onset MLD, parents are often forced to give up work to care for their affected children. The aim of this study was to determine the lost family income due to caring for early-onset MLD patients, and productivity gains associated with a potential gene therapy treatment from a US perspective.

Data from a cross-national MLD caregiver survey were used to inform US specific inputs for changes in employment status together with lost family income derived from the mean annual salaries and number of working days in the US in 2022. Future productivity gains were calculated using the Human Capital Approach. Due to lack of employment data in MLD patients, published data from cerebral palsy and Down’s syndrome were utilised as proxies to estimate the impact of motor and cognitive dysfunction on employment, alongside expected earnings based on the US education levels of achievement. A 3.0% discount rate was used to adjust productivity gains and lost family income for time preference.

The results demonstrate that substantial family income is lost, with the estimated family income lost as a result of caring for an untreated MLD patient as high as $470,137. The most significant losses were reported in the later stages of MLD. Further, there are considerable productivity gains for patients after treatment, compared to untreated, with productivity gains accrued over a working life estimated to be up to $640,972.

In conclusion, the positive impact a gene therapy for the treatment of MLD confers on the societal costs are substantial.