Hypophosphatasia, infantile

Hypophosphatasia, Infantile is a rare, inherited, metabolic disorder characterized by defective bone mineralization and a deficiency in the enzyme alkaline phosphatase. This condition is a form of Hypophosphatasia which specifically affects infants and is caused by mutations in the ALPL gene, which encodes the tissue-nonspecific isoenzyme of alkaline phosphatase. The disease manifests shortly after birth with severe clinical symptoms.

Symptoms and Signs

Infantile hypophosphatasia presents with a wide range of symptoms, primarily affecting the bones and teeth. Key symptoms include:

• Rickets-like bone deformities
• Premature loss of deciduous (baby) teeth, which is particularly notable as the teeth may be lost with little to no root resorption
• Respiratory complications due to chest deformities
• Hypotonia (reduced muscle tone)
• Failure to thrive
• Seizures, which are often related to Hypocalcemia (low calcium levels in the blood)

Causes

The primary cause of infantile hypophosphatasia is mutations in the ALPL gene. This gene is crucial for the production of alkaline phosphatase, an enzyme that plays a significant role in the process of bone mineralization. Mutations in the ALPL gene lead to reduced activity or complete absence of this enzyme, resulting in the symptoms associated with the disorder.

Diagnosis

Diagnosis of infantile hypophosphatasia involves a combination of clinical observation, biochemical tests, and genetic testing. Key diagnostic tests include:

• Measurement of serum alkaline phosphatase activity, which is typically significantly lower in affected individuals
• Genetic testing for mutations in the ALPL gene
• X-rays and other imaging techniques to observe bone abnormalities

Treatment

There is no cure for infantile hypophosphatasia, but treatment focuses on managing symptoms and preventing complications. Treatment options may include:

• Enzyme replacement therapy (ERT) with asfotase alfa, a drug that aims to replace the deficient enzyme in patients
• Supportive care for respiratory complications
• Nutritional support to promote growth and manage hypocalcemia
• Physical therapy to strengthen muscles and improve motor skills

Prognosis

The prognosis for infants with hypophosphatasia varies widely and depends on the severity of the disease. The infantile form is generally considered more severe than other forms, with a significant risk of life-threatening complications. However, early diagnosis and treatment can improve the quality of life and survival rate for affected individuals.

See Also

• Metabolic Bone Disease
• Genetic Disorders
• Enzyme Deficiency

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