Pipecolic acidemia

Pipecolic acidemia (also known as hyperpipecolic acidemia or hyperpipecolatemia) is an extremely rare inborn error of metabolism characterized by elevated levels of pipecolic acid in the blood, urine, and cerebrospinal fluid. Pipecolic acid is an intermediate in the degradation pathway of lysine, and its accumulation reflects a defect in peroxisomal function or in the specific enzyme L-pipecolic acid oxidase. The condition primarily affects the central nervous system and liver. Clinical features typically present in infancy or early childhood and include progressive neurological deterioration, hepatomegaly (enlarged liver), intellectual disability, seizures, hypotonia (low muscle tone), and developmental delay. Some patients may also exhibit facial dysmorphism and visual impairment. The neurological involvement is often severe and progressive, leading to significant disability. Pipecolic acidemia shares biochemical and clinical overlap with peroxisomal biogenesis disorders such as Zellweger spectrum disorders, in which elevated pipecolic acid is a secondary finding. Isolated pipecolic acidemia as a distinct entity remains debated in the literature, and some cases may represent milder variants of peroxisomal disorders. There is no specific curative treatment currently available. Management is supportive and symptomatic, focusing on seizure control, nutritional support, physical therapy, and developmental interventions. Dietary restriction of lysine has been attempted in some cases but with limited evidence of efficacy. Prognosis varies but is generally poor in severe forms, with significant morbidity related to progressive neurological decline.

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