Hyperlysinuria with hyperammonemia. Periodic Hyperlysinemia.
Incidence
Possible autosomal recessive.
Clinical Characteristics
Brown et al. (1972) described a physically and mentally retarded child with dibasicaminoaciduria and hyperammonemia. Oral loading tests showed diminished capacity for absorbing lysine. Fasting blood arginine and lysine concentrations were low. Postprandial hyperammonemia was thought to be due to deficiency of arginine to serve as substrate for urea cycle activity. The defect in intestinal absorption distinguishes this disorder from familial protein intolerance. In periodic hyperlysinemia, normal protein intake results in hyperlysinemia and high protein intake or administration of a lysine load precipitates severe hyperammonemia and coma. Hyperammonemia is thought to result from the elevated levels of lysine competitively inhibiting arginase, which catalyzes the last step in urea formation. A partial deficiency (25% of normal) of L-lysine dehydrogenase, the enzyme that converts lysine to an alpha-keto-epsilon aminocaproic acid, has been demonstrated in a liver biopsy from a single patient (a 3-month-old girl) (Ghadimi, 1978). No information is available on the genetics of this disorder.
Precipitants
In periodic hyperlysinemia, normal protein intake results in hyperlysinemia. However high protein intake or administration of a lysine load precipitates severe hyperammonemia and coma.
Provocation Tests
Oral loading tests in the past showed diminished capacity for absorbing lysine. In periodic hyperlysinemia, normal protein intake results in hyperlysinemia and high protein intake or administration of a lysine load precipitates severe hyperammonemia and coma. It probable should not be attempted.
Diagnostic Procedures
Quantitative aminoacids in plasma and urine. Ammonia levels. L-lysine dehydrogenase partial deficiency may be present.