PBD8B is a mild presentation in the Zellweger spectrum of peroxisome biogenesis disorders. The spectrum includes Neonatal adrenoleukodystrophy and Infantile Refsum disease which were earlier considered distinct disorders. Patients with PBD8B suffer from neurologic abnormalities such as progressive leukodystrophy, reduced cerebral and cerebellar volume, atrophy of the cerebellar vermis, and corpus callosum and mild cerebellar signs. This results in cognitive impairment, ataxia, spastic paraparesis, dysarthria, dysmetria, and dysphagia. The disorder also causes ocular anomalies such as nystagmus, low vision aids, cataracts, abnormal saccades, and optic atrophy. PBD8B is a progressive condition. While patients exhibit normal growth and development in the first year of life, they become wheelchair dependent within the first decade. Patients with infantile refsum disease may reach adulthood. However, those suffering from neonatal adrenoleukodystrophy generally succumb to the disease in their teens.
The diagnosis of peroxisome biogenesis disorders is commonly made by biochemical tests that identify elevated levels of Very Long Chain Fatty Acids (VLCFA), phytanic acid, pristanic acid, and bile acid intermediates in the blood or urine. Once these biochemical abnormalities are detected, they are subsequently confirmed in cultured fibroblasts. Studying the patient’s fibroblasts for markedly enlarged peroxisomes can also help in diagnosis as PBD8B sufferers usually only exhibit mild elevations in their biochemical tests. Treatment of PBD8B focuses on symptomatic therapy. Patients may require gastrostomy feeding tubes, low vision aids, cataract surgery and anti-seizure medication.