La leucinose : définition, formes cliniques, diagnostic, prise en charge thérapeutique et diététique | Maple syrup urine disease : Definition, clinical forms, diagnosis, therapeutic and dietetic management

Maple syrup disease (MSD) is a rare autosomal recessive disorder caused by a decreased activity of branched-chain-ketoacid dehydrogenase, the second enzyme in the pathway of degradation of branched-chain aminoacids (leucine, isoleucine and valine). The three main clinical forms described are : classical form, at the neonatal period, marked by a severe neurological toxicity, subacute form appearing later and thiamine sensitive form. In every case, diagnosis is based on an increase of leucine, isoleucine and valine in blood and urines, with an associated presence of alloisoleucine. Diagnosis is confirmed by molecular analysis of corresponding genes. In several situations of protein catabolism, episodes of intoxication can occur. Emergency treatment for neonates and acutely sick children or adults uses hypoenergetic artificial nutrition (parenteral or enteral nutrition) without aminoacids and consequently involving only glucido-lipidic nutriments. Forty-eight hours later, proteins are progressively reintroduced. Natremia must be controlled, and a supplementation with isoleucine et valine is mandatory. Hemodialysis or hemofiltration can be necessary. Chronic treatment needs a strictly limited diet concerning branched-chain aminoacids. Natural proteins are limited as well as fruits and vegetables intakes. Lipids and sweetened food are permitted ad libitum. Food is supplemented by hyprotidic produces available in some hospital pharmacies. Oncoming of deficiencies is prevented by suplementations in minerals, vitamins, trace-elements, n–3 fatty acids and non-essential aminoacids. Follow-up is performed for children by a pediatrist and by an informed practitioner for adults. Psychomotricity and growth of children must be as normal as possible. All along the life, a metabolic equilibrium is needed and nutritional assessments are recommended at least once a year. Blood leucine level is regularly measured. A diagnosis before birth is possible when MSD has been identified in a member of the family. Pregnancy must be carefully prepared and followed.