Neonatal seizures and severe hypotonia in a male infant suffering from a defect in peroxisomal beta-oxidation

Abstract

In this paper, we describe a baby male born to healthy non-consanguineous parents presenting at birth with hypotonia and seizures. Additional salient clinical features included the development of glaucoma, the absence of significant facial dysmorphism and the absence of liver enlargement or renal cysts. The patient died at the age of 3 months. At autopsy, liver fibrosis and kidney glomerulosclerosis were noted. Neuropathological findings included pachygyria of the olivary nuclei and cerebellar neuronal heterotopias. There was no evidence for a demyelinating process. Biochemically, the patient was found to have elevated plasma levels of very-long-chain fatty acids (VLCFA) and abnormal bile acid intermediates, whereas other indicators of peroxisomal function (plasmalogen biosynthesis and plasma pipecolic acid) were normal. Catalase staining of a liver biopsy specimen revealed peroxisomes to be present in normal numbers, although some were abnormally large. Trilamellar inclusions typical of a peroxisomal fatty acid oxidation defect were present in macrophages. Indeed, beta-oxidation of the very-long-chain fatty acid hexacosanoic acid (C26:0) was found to be strongly deficient. Fatty acyl-CoA oxidase activity in the patient's liver was normal, however. Furthermore immunocytochemical studies using antibodies against acyl-CoA oxidase, bifunctional protein and peroxisomal thiolase, revealed the normal localization of all three enzyme proteins within the peroxisomes. We suggest that our patient has a selective peroxisomal beta-oxidation defect, a recently identified heterogeneous group of early-onset peroxisomal disorders distinct from the Zellweger syndrome and other generalized peroxisomal disorders.