Medium/short-chain 3-hydroxyacyl-CoA dehydrogenase (M/SCHAD) deficiency
M/SCHAD deficiency is inherited in an autosomal recessive pattern. Normally a person has two functional HADH genes. In people with M/SCHAD deficiency, both genes have a mutation and there is a deficiency of the critical enzyme activity. Each parent of a newborn with M/SCHAD deficiency typically has one functional and one mutated gene and is considered a carrier. When both parents are carriers, the chance of a newborn inheriting two mutated genes is 25%.
Carriers of M/SCHAD deficiency do not typically have symptoms.
People with M/SCHAD deficiency usually have hyperinsulinism (increased insulin), which causes hypoglycemia (low blood sugar). Symptoms may include vomiting, diarrhea, and lethargy. There have also been reports of hypotonia (muscle weakness) and liver problems.
- Incidence: The overall incidence is unknown, but M/SCHAD deficiency is very rare with only a small number of patients reported in the literature.
- New York State Method of Screening (First Tier): Screening for M/SCHAD deficiency is accomplished by measuring acylcarnitines (C4OH and C6OH) by tandem mass spectrometry (MS/MS).
- Second Tier Screening: None
- Testing can be affected by: None known
- Interpretation/reporting of data: Results are reported as screen negative, borderline or as a referral. A repeat specimen should be collected for a borderline result. Prompt consultation with a specialist is required for a referral.
- Referral to Specialty Care Center: Patients with an abnormal newborn screen for M/SCHAD deficiency are referred to an Inherited Metabolic Disorder Specialty Care Center for evaluation by a biochemical geneticist trained in the diagnosis and treatment of M/SCHAD deficiency.
Diagnostic testing may include quantification of plasma acylcarnitines, molecular genetic testing of the gene and functional analysis of fatty acid oxidation on fibroblasts (skin cells).
Treatment may include an oral medication, diazoxide. Treatment may also be dietary management including avoidance of fasting.
Prognosis is variable and dependent on multiple factors, including the severity of disease and response to treatments.
Medium/short-chain 3-hydroxyacyl-CoA dehydrogenase (M/SCHAD) deficiency is a fatty acid oxidation disorder (inherited metabolic disorder).
M/SCHAD deficiency is caused by mutations in the HADH genes. Individuals with this disorder are unable to convert certain fats to energy and may develop symptoms during times of high energy need such as fasting or illness.