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Muscular carnitine palmitoyltransferase II deficiency in infancy
H Hurvitz1, A Klar, I Korn-Lubetzki
1Department of Pediatrics, Bikur Cholim General Hospital, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Insights
Carnitine palmitoyltransferase (CPT) II deficiency can cause myoglobinuria in infants. This case highlights a unique, severe presentation linked to impaired fatty acid oxidation, suggesting other genetic factors may influence disease severity.
Area of Science:
- Biochemistry
- Genetics
- Pediatrics
Background:
- Carnitine palmitoyltransferase II (CPT II) deficiency is an inherited metabolic disorder.
- It typically affects fatty acid oxidation, crucial for energy production.
- Infantile presentations are often severe, but variable.
Observation:
- An 8-month-old female presented with acute febrile myoglobinuria.
- Fibroblast analysis revealed significantly reduced CPT II activity (16% of control) and impaired long-chain fatty acid oxidation (25% of control).
- Genetic testing identified homozygosity for the common S113L mutation in the CPT II gene.
Findings:
- The patient's severe phenotype and early onset were unusual, given that residual CPT II activity >10% and homozygosity for S113L typically correlate with milder disease and later onset.
- Marked impairment of long-chain fatty acid oxidation was observed, suggesting potential involvement of other genetic factors.
- This case underscores the variability in CPT II deficiency presentations.
Implications:
- CPT II deficiency should be considered in the differential diagnosis of isolated myoglobinuria in infants.
- The findings highlight the complex interplay between genotype and phenotype in metabolic disorders.
- Further research into modifier genes may elucidate the mechanisms behind variable disease severity in CPT II deficiency.
Abstract:
An 8-month-old female presented with febrile myoglobinuria. The activity of carnitine palmitoyltransferase (CPT) II was decreased to 16% of the control mean, and the oxidation of the long-chain fatty acids was reduced to 25% of the mean in the fibroblasts. Homozygosity for the common mutation, S113L, was identified in the CPT II gene. Residual CPT II activity of more than 10% of the mean and homozygosity for the common mutation S113L are usually associated with a milder reduction of long-chain fatty acid oxidation to about 80% of the control and with a later age of clinical onset. The early clinical presentation in the present patient is unique and was associated with a marked impairment of long-chain fatty acid oxidation, possibly because of other genetic factors. CPT II deficiency should be included in the differential diagnosis of isolated myoglobinuria in infancy.