D-Cycloserine for Serine Palmitoyltransferase Inhibition: Treatment of a Single Patient With a Complex Hereditary Spastic Paraplegia Due to a De Novo Variant in the SPTSSA Gene

At each visit a medication reconciliation will be performed which will include medications, vitamins, herbal preparations, and supplements. For each medication the investigators will record start and end dates of administration, dosage, frequency, and reason for use. After the initial medication reconciliation the investigators will review the participant's medications with pharmacy to determine if any significant drug-drug interactions exist between the participant's medications and D-Cycloserine. If such interactions are discovered the investigators will collaborate with the participant's prescribing physician to determine if dose alterations/discontinuation would benefit the participant while receiving D-Cycloserine therapy. For subsequent medication reconciliations at follow up visits the investigators will do the same for any new medications that the participant may be taking.

After clinical assessments, the investigators will routinely return results to the participant by phone or by secure messaging in the EMR (per standard clinical protocol).

In addition to the scheduled study visits the participant is encouraged to follow up with the the investigators via phone or by secure messaging in the EMR should they have any questions or updates about interval changes in the participant's clinical status. Each report will be assessed by the investigators and based on their clinical judgement the participant may require additional follow up evaluations.

If the results are acceptable and there is no contraindication to treatment the investigators will begin dosing D-Cycloserine following the baseline visit.

The D-Cycloserine (250 mg) capsules will be compounded to a suspension of 25 mg/mL, and for a starting dose the participant would take 15 mg/kg (253 mg = 10.1 mL) by mouth once daily. Throughout the study, based on serial clinical evaluations, sphingolipid levels, and toxicity monitoring the investigators will adjust the dose between 15-20 mg/kg/day at the discretion of the Principle Investigator (PI). The PI reserves the right to stop, temporarily hold, or adjust the dose of the medication at their discretion. As the participant grows and gains weight the investigators will adjust the dose as necessary in order to keep it at the goal of 15 to 20 mg/kg/day.