Adult Refsum Disease: Case Series of Reducing Circulating Phytanic Acid Levels With Dietary Interventions

Adult Refsum disease (ARD, OMIM #266510) is an autosomal recessive condition, resulting in phytanic acid (PA) accumulation in plasma and tissue. The management of ARD relies on a low PA diet, but the importance of adequate energy and carbohydrate provision in reducing circulating PA levels and preventing metabolic crisis is less well described. Two patients recently diagnosed with ARD initiated on the low PA diet leading to a 65% reduction in circulating PA levels, one case achieving this reduction in 5 months. Four patients already established on the low PA diet for > 10 years experienced a rapid rise in circulating PA levels due to weight loss and/or inadequate carbohydrate intakes, despite adherence to a low PA diet. Circulating PA levels more than doubled in all four of these cases. Implementing dietary interventions to ensure adequate energy, carbohydrates and weight stabilisation resulted in a decrease in circulating PA levels by 47%-84% in the outpatient setting. The reduction in circulating PA occurred within 1.6-5 months. These cases demonstrate that PA restriction, and weight and carbohydrate management have integral roles in ensuring metabolic stability in ARD. This case series highlights that circulating PA levels can be reduced more rapidly with dietary interventions than previously shown in case series of chronic management.