Sujet de la discussion : MedeSpace.Net :: United State Médical Licensing Examination

Publié par La Pharmacienne le 13-02-2009 18:50
#23

Question 02 :
A 12-year-old healthy Jewish girl is found on routine blood count to have a mild anemia, leukopenia, and thrombocytopenia. Physical examination reveals an enlarged spleen. An x-ray of the femur is described as "appearing to be an Erlenmeyer flask." Bone marrow examination shows abnormal cells. The diagnosis can be confirmed by measurement of activity of which of the following?

a- Sphingomyelinase activity
b- Hexosamidase A
c- Sulfatase A
d- Glucocerebrosidase
e- Ceramide trihexosidase

Jewish = juive
enlarged spleen = splenomegalie
x-ray = radiographie standard
Erlenmeyer flask = flacon d'Erlenmeyer
Bone marrow = Moelle osseuse

Answer to Question 02 :
The answer is d, Glucocerebrosidase.[3-4]
>>> Gaucher disease is characterized by a glucocerebrosidase deficiency, which causes an abnormal accumulation of glucocerebroside in the reticuloendothelial system. Bone marrow aspirate shows the typical Gaucher cells engorged with glucocerebroside. Replacement of marrow with these cells leads to anemia, leukopenia, and thrombocytopenia. The liver and spleen can also be involved. Serum acid phosphatase is elevated. X-ray demonstrates an Erlenmeyer-flask appearance of the long bones. The diagnosis of Gaucher disease is confirmed by the absence of glucocerebrosidase activity in leukocytes, in cultured skin fibroblasts, and in liver cells. Prenatal diagnosis by enzyme analysis is now possible. In the most common form of Gaucher disease, adult type I, there is no involvement of the central nervous system. Therefore, MRI of the brain is not indicated.

Sphingomyelinase deficiency causes type A Niemann-Pick disease; hexosaminidase A deficiency causes Sandhoff disease; sulfatase A deficiency causes juvenile metachromatic leukodystrophy; and serum trihexosidase causes Fabry disease


References
1- Behrman RE, Kliegman RM, Jenson HB, eds. Nelson Textbook of Pediatrics. 17th ed. Philadelphia: WB Saunders Co.; 2003: 402-404, 469-471, 475-477, 1323.
2- Rudolph CD, Rudolph AM, Hostetter MK, Lister G, Siegel NJ, eds. Rudolph's Pediatrics. 21st ed. New York: McGraw-Hill; 2003: 612, 1487-1488, 1490-1491, 1542-1543, 1996-1997.
3- Behrman RE, Kliegman RM, Jenson HB, eds. Nelson Textbook of Pediatrics. 17th ed. Philadelphia: WB Saunders Co.; 2003: 463-464.
4- Rudolph CD, Rudolph AM, Hostetter MK, Lister G, Siegel NJ, eds. Rudolph's Pediatrics. 21st ed. New York: McGraw-Hill; 2003: 2326-2328.