Carnosinemia

A rare metabolic disorder

Carnosinemia
Synonyms	Carnosinase deficiency, Aminoacyl-histidine dipeptidase deficiency
Pronounce
Field	Metabolic disorders, Medical genetics
Symptoms	Developmental delay, hypotonia, seizures, intellectual disability, tremors
Complications	Neurological impairment, motor coordination difficulties
Onset	Infancy
Duration	Lifelong
Types
Causes	Mutations in the CNDP1 gene leading to carnosinase enzyme deficiency
Risks	Autosomal recessive inheritance
Diagnosis	Urine and plasma amino acid analysis, genetic testing
Differential diagnosis	Other metabolic disorders, neuromuscular disorders
Prevention	None known
Treatment	Supportive care, physical therapy
Medication	Anticonvulsants for seizure control (if applicable)
Prognosis	Varies; may lead to lifelong neurological issues
Frequency	Extremely rare
Deaths	Rare; dependent on severity of neurological complications

Carnosinemia has an autosomal recessive pattern of inheritance.

Carnosinemia is a rare metabolic disorder characterized by elevated levels of carnosine in the blood and urine. This condition is caused by a deficiency of the enzyme carnosinase, which is responsible for breaking down carnosine into its constituent amino acids, beta-alanine and histidine.

Pathophysiology

Carnosinemia results from a deficiency in the enzyme carnosinase, specifically the cytosolic form known as CNDP1. Carnosinase is responsible for the hydrolysis of carnosine, a dipeptide composed of beta-alanine and histidine. In individuals with carnosinemia, the lack of functional carnosinase leads to the accumulation of carnosine in the blood and urine.

Carnosine is found in high concentrations in muscle and brain tissues, where it plays a role in buffering pH and acting as an antioxidant. However, its accumulation in the bloodstream due to carnosinase deficiency can lead to various neurological and developmental symptoms.

Clinical Features

The clinical presentation of carnosinemia can vary, but common symptoms include:

• Developmental delay
• Intellectual disability
• Seizures
• Hypotonia (reduced muscle tone)
• Ataxia (lack of voluntary coordination of muscle movements)

The severity of symptoms can vary widely among affected individuals, and some may present with only mild symptoms.

Diagnosis

Diagnosis of carnosinemia is typically made through biochemical analysis of blood and urine, revealing elevated levels of carnosine. Genetic testing can confirm mutations in the CNDP1 gene, which encodes the carnosinase enzyme.

Treatment

There is currently no specific treatment for carnosinemia. Management of the condition is primarily supportive and symptomatic. This may include:

• Anticonvulsant medications to control seizures
• Physical therapy to improve motor skills and muscle tone
• Special education programs to address developmental delays

Prognosis

The prognosis for individuals with carnosinemia varies depending on the severity of the symptoms. Early intervention and supportive therapies can improve quality of life and developmental outcomes.

Related pages

• Metabolic disorder
• Amino acid
• Enzyme deficiency
• Neurological disorder