Which enzyme is deficient in Marfan's syndrome?
Marfan syndrome is caused by mutations in the FBN1 gene on chromosome 15, which encodes a glycoprotein called fibrillin-1, which is essential for the proper formation of the extracellular matrix including the biogenesis and maintenance of elastic fibers. Elastin fibers are found throughout the body but are paicularly abundant in the aoa, ligaments and the ciliary zonules of the eye, consequently these areas are among the worst affected. Although there are no unique signs or symptoms of Marfan syndrome, the constellation of long limbs, dislocated lenses, and aoic root dilation is sufficient to make the diagnosis with confidence. A. Skeletal System The most readily visible signs are associated with the skeletal system. Many individuals with Marfan Syndrome grow to above average height and may have long slender limbs with fingers and toes that are also abnormally long and slender (arachnodactyly). This long, slender body habitus and long, slender limbs are known as dolichostenomelia. Abnormal curvature of the spine (scoliosis) is common, as is abnormal indentation (pectus excavatum) or protrusion (pectus carinatum) of the sternum. B. Eyes Nearsightedness and astigmatism are common, but farsightedness can also result. Subluxation (dislocation) of the crystalline lens in one or both eyes (ectopia lentis) also occurs In Marfan's the dislocation is typically superotemporal whereas in the similar condition homocystinuria, the dislocation is inferonasal. Sometimes weakening of connective tissue may cause detachment of the retina Early onset glaucoma can be another complication. C. Cardiovascular System The most serious conditions associated with Marfan syndrome involve the cardiovascular system. The major sign is a dilated aoa or an aoic aneurysm. Because of the underlying connective tissue abnormalities that cause Marfan syndrome, there is an increased incidence of dehiscence of prosthetic mitral valve. During pregnancy, even in the absence of preconceived cardiovascular abnormality, women with Marfan syndrome are at significant risk of acute aoic dissection, which can be lethal if untreated. For this reason, women with Marfan syndrome should receive a thorough assessment prior to conception, and echocardiography should be performed every 6-10 weeks during pregnancy, to assess the aoic root diameter. D. Lungs Marfan syndrome is a risk factor for spontaneous pneumothorax. Marfan syndrome has also been associated with sleep apnea and idiopathic obstructive lung disease. E. Central nervous system Another condition that can reduce the quality of life for an individual, though not life-threatening, is dural ectasia, the weakening of the connective tissue of the dural sac. Other spinal issues associated with Marfan include degenerative disk disease and spinal cysts. Following disorders have similar signs and symptoms of Marfan syndrome: Congenital Contractural Arachnodactyly (CCA) or Beals Syndrome Ehlers-Danlos syndrome Homocystinuria Loeys-Dietz syndrome MASS phenotype Stickler syndrome Multiple endocrine neoplasia, type 2B.
Cystathione B synthetase
Lysyl oxidase
Collagenase
None of the above