Metabolic syndromes: cardiac syndromes
May be the dominant or only clinical problem in a variety of IMDs.
Pompe disease (GSD II)—presents in early infancy with marked skeletal myopathy, mas-sive cardiomegaly (large QRS, left axis deviation, shortened PR, T-wave inversion).
• Systemic carnitine deficiency: presents with skeletal myopathy, hypotonia encephalopathy, hepatic syndrome (hepatomegaly, hypoglycaemia, hepatocellular dysfunction).
• Long or very long chain acyl-CoA dehydrogenase deficiency: presents with myopathy, exercise intolerance with myoglobinuria, hypotonia, encephalopathy, hepatic syndrome 9 hyperammonaemia.
Propionic acidaemia— intermittent metabolic acidosis; ketosis; hyperammonaemia; neutropenia.
Fabry disease— chronic neuritis pain in hands and feet; angiokeratomata; corneal opacities; pro-gressive renal failure; cardiac arrhythmias (intermittent SVT); cerebrov-ascular disease.
• Plasma: lactate; carnitine (free and total); acylcarnitine profile; ammonium; liver function tests; urea, creatinine, and electrolytes
• Urine: organic acids
Fibroblast cultures; enzyme studies
• Plasma: lactate/pyruvate ratio
• CSF: lactate
• Imaging: MRI
• Electrophysiology: evoked potentials
• Tissue: muscle and skin biopsy studies
• Urine: mucopolysaccharide and oligosaccharide screen, glycolipids
• Imaging: skeletal radiology
Blood: lysosomal enzyme studies
IMD-related cardiomyopathy may be complicated by arrhythmias includ-ing:
• Heart block: mitochondrial cytopathy; Fabry disease; carnitine– acylcarnitine translocase (CACT) deficiency; propionic acidaemia.
• Tachyarrhythmia: fatty acid oxidation defects; CACT.
CAD occurs in Fabry disease, familial hyperlipidaemias, and familial hyper-cholesterolaemia (FH).
FH affects 1/500 individuals with the following effects.
• Homozygotes: severe cholesterolaemia; ischaemic heart disease in infancy or childhood; cholesterol accumulation in the skin (tuberous xanthomas, subcutaneous nodules); and arcus senilis.
• Heterozygotes: fatal myocardial infarction in third decade.
Familial hyperlipidaemias causing premature CAD include the following.
• Type IV: hyperlipidaemia (increased very low-density lipoproteins).
• Type IIa, familial hypercholesterolaemia: hypercholesterolaemia (increased low-density lipoproteins) with tuberous xanthomas, tendinous xanthomas, and arcus senilis.
• Type IIb: combined hyperlipidaemia (increased low- and very low-density lipoproteins).
Type III, familial dysbetalipoproteinaemia: B-very low-density lipoproteins with eruptive tuberous xanthoma, planar xanthomas, peripheral vascular disease.