TN 7 (08-12)
DI 23022.770 Hypophosphatasia--Perinatal (Lethal) and Infantile Onset Types
COMPASSIONATE ALLOWANCE INFORMATION
HYPOPHOSPHATASIA--PERINATAL (LETHAL) and INFANTILE ONSET TYPES
Alkaline Phosphotase Deficiency; Perinatal Lethal Hypophosphatasia; Hypophosphatasia Perinatal Lethal Form; Perinatal Rathburn Disease; Phosphoethanolaminuria
Hypophosphatasia is a rare, inherited metabolic disorder that affects the development of bones and teeth. There are several forms of this disorder, with the perinatal (lethal) and infantile onset types being the most severe. Both of these forms are characterized by hypercalcemia; malformed, weakened, and softened bones; and multiple congenital abnormalities, leading to respiratory failure.
DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND ICD-9-CM CODING
Diagnostic testing: Diagnostic testing consisting of subnormally low activity of tissue non-specific alkaline phosphatase (TNALP) enzyme in serum; bone imaging of the bones shows severe demineralization, especially in the metaphyses (the wider part at the extremity of the shaft of a long bone).
Physical findings: There is a near absence of skeletal mineralization. Fractures are often present. Skin-covered spurs of the knees and elbow joints may also be present. Physical examination shows large fontanels, shortened bones, chest deformities, and muscle weakness.
ONSET AND PROGRESSION
For perinatal (lethal) onset hypophosphatasia, death occurs either in-utero or within the first months of life. Infantile onset hypophosphatasia presents within the first year of life, and has 50% mortality. The cause of death is usually due to respiratory failure. Perinatal (benign) hypophosphatasia type is characterized by prenatal skeletal manifestations that slowly resolve into the milder childhood and adult onset hypophosphatasia types, which have variable clinical courses.
Currently there is no cure or definitive treatment for this disorder.
SUGGESTED PROGRAMMATIC ASSESSMENT*
Suggested MER for evaluation:
Clinical history and examination that describes the diagnostic features of the impairment
Laboratory testing for identified enzyme changes
Imaging documenting decreases in bone mineralization
Suggested Listings for Evaluation:
Evaluate the perinatal (lethal) onset type of hypophospatasia, under listing 110.08A. Evaluate perinatal (benign), child, and adult onset hypophosphatasia types on a case-by-case basis.
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* Adjudicators may, at their discretion, use the Medical Evidence of Record or Listings suggested to evaluate the claim. However, the decision to allow or deny the claim rests with the adjudicator.