Dietary Management of Classical Homocystinuria: Challenges and Solutions
Dietary management is crucial for individuals with classical homocystinuria (CBS deficiency), involving a low-protein diet and supplements to optimize homocysteine and methionine levels. The treatment differs for babies and older patients, each requiring specific considerations. Despite the necessity for dietary adjustments, challenges such as distance to specialist centers, needle phobia, and expense can hinder compliance. Factors like diagnosis timing, adolescence, family attitudes, and personality play roles in compliance. Newborn screening and betaine supplementation can aid in achieving optimal control. Overall, adherence to dietary protocols is essential for managing classical homocystinuria effectively.
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Presentation Transcript
Dietary management of classical homocystinuria (CBS deficiency) Andrew Morris
Dietary protein Protein synthesis Methionine Homocysteine Pyridoxine CBS Homocysteine formation is minimised by giving enough methionine for protein synthesis but not much more This needs a very low-protein diet & supplements of the other amino acids
Dietary treatment of babies Combination of Special formula that contains All the normal ingredients except protein All the amino acids except methionine Breast milk or normal infant formula To supply methionine for protein synthesis Proportions of the two are adjusted to optimise blood homocysteine & methionine levels
Dietary treatment of older patients Small, measured amounts of food containing protein Methionine-free amino acid mixture Adequate energy from low protein foods most fruit & vegetables synthetic e.g. low-protein bread, biscuits, pasta Vitamin & mineral supplements (included in most amino acid mixtures) Adjusted to optimise homocysteine & methionine
Challenges in dietary treatment Distance to specialist centre Telephone advice & taking blood locally or measuring homocysteine in bloodspots can reduce number of visits Needle phobia may hamper monitoring Play therapists can help to overcome this Expense & (relative) unpalatability of supplements & low-protein foods Health insurance & medical food companies should be lobbied over these issues Restrictions are unpopular leading to poor compliance
Factors contributing to poor compliance Diagnosis after infancy Adolescence Attitude of family & friends Personality Newborn Screening can detect most patients with pyridoxine-unresponsive homocystinuria Addition of Betaine can help if unable to reach homocysteine targets with diet alone (Betaine alone seldom achieves adequate control)
Dietary protein Protein synthesis Methionine Betaine Homocysteine CBS Side effects of betaine Taste, fishy odour at high doses Methionine rises, seldom toxic but keep <1000 umol/l
