The most common clinical syndromes associated with 3-methyl-glutaconic (MGC) aciduria are reviewed by researchers from various centers; Courtwright and Summers Metabolic Disease Center and Baylor Research Institute, Dallas, TX; Shaare Zedek Medical Center, Jerusalem; Free University of Amsterdam; Loewenstein Hospital, Tel-Aviv Univ, Raanana, Israel; and Kennedy Krieger Institute, Baltimore, MD. Three distinct syndromes are described: Type I 3-MG-CoA Hydratase Deficiency.- (autosomal recessive) 3 patients had delayed speech and macrocephaly, increased urinary excretion of 3-MGC acid, 3-M Glutaric(MGR) and 3-hydroxyisovaleric acids, elevated CPK and serum carnitine, and hypoglycemia. Urinary 3-MGC excretion is decreased by restriction of L-leucine intake. Type II Barth Syndrome.- (X-linked) dilated cardiomyopathy, recurrent infection, neutropenia, growth retardation. Improves with age. Increased urinary excretion of 3-MGC, 3-MGR, fumaric, and 2-ethylhydracrylic acids. Type III Costeff Optic Atrophy Syndrome.- (autosomal recessive) A Behr-like syndrome described in 39 patients of Iraqi-Jewish origin living in Israel. Optic atrophy, choreoathetosis, spastic paraparesis, cerebellar ataxia. Nonprogressive. 3-MGC and 3-MGR aciduria.
An Unclassified 3-MGC aciduria includes patients presenting in the first year of life with neurologic impairment, seizures, retinal pathology, and a fatal course. Cardiomyopathy, hepatic dysfunction, hypoglycemia, lactic acidosis, and dysmorphia are associated manifestations. Defects of the mitochondrial respiratory chain are suggested. 
COMMENT. This review will assist the neurologist in the differential diagnosis of patients with 3-MGC aciduria. Some cases are multisystemic and progressive, with onset from birth to several years, some are primarily neurologic and non-progressive, while others involve the heart muscle and may improve with age.