Icahn School of Medicine at Mount Sinai
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Genetic Testing Lab

Test Catalog Biochemical Genetics Laboratory Hexosaminidase B

Hexosaminidase B

Test Description:
Sandhoff disease is a rare, recessively inherited neurodegenerative disorder caused by a deficiency of beta-hexosaminidase A and B that leads to a pathological accumulation of GM2 ganglioside. This disorder is clinically similar to Tay-Sachs disease. Features include progressive loss of coordination, seizures, difficulty swallowing and poor pulmonary function. Affected individuals eventually become blind, severely mentally retarded, paralyzed and unaware of their surroundings. Onset is typical at approximately 6 months of age, and average life expectancy is 3 years. Sandhoff disease is a panethnic condition, with a carrier frequency of 1 in 600 to 1 in 1000. This assay can detect approximately 98% of carriers of Sandhoff disease. Enzyme analysis is performed by measuring hexosaminidase A activity in serum and leukocytes. Hexosaminidase A is present in all tissues and is comprised of two subunits, Hex A and Hex B. Hexosaminidase A% activity is measured (using a fluorescent synthetic substrate) by comparing total activity to heat inactivatable (i.e., hex A) activity.

Specimen Requirements:
Two 5 – 10 ml ACD (yellow top) tubes are preferred.  Sodium (or Lithium) heparin (green top) tubes or EDTA (purple top) tubes are also acceptable.  

Shipping:
Ship whole blood at room temperature.  Blood samples must be received within 72 hrs of collection.  If the sample cannot be sent immediately, prepare and freeze plasma (serum) and leukocyte pellets until shipment and ship frozen on dry ice.

Turnaround Time: 10-14 days

CPT Codes: 80500, 83080x2, 82657x2, 84155

Consent Form: Biochemical Consent [PDF]

Requisition Form: General Test Requisition [PDF]