Rheum| Systemic Lupus Erythematosus

4.04 Systemic Lupus Erythematosus Rheumatology review for the USMLE Step 1 Exam Marfan's syndrome, Ehlers-danlos, and homocystinuria are three distinct diseases that affect connective tissue. They share some clinical features like tall stature, long fingers, scoliosis, high arched pallet, chest wall deformities, joint hypermobility, and lens dislocation. Marfans is caused by a mutation in the FBN1 gene, resulting in defective fibrillin-1, and the main complication is aortic root dilation. Homocystinuria is a metabolic disorder caused by a defect in homocysteine breakdown, leading to elevated levels of homocysteine, and the main complication is thrombosis. Ehlers-Danlos is caused by a deficiency in type III collagen, and the main complication is vascular rupture. Marfans has an upward lens dislocation, homocystinuria has a downward lens dislocation, and Ehlers-Danlos has hyperextensible skin and joint hyperextensibility. Marfans usually presents in teens, homocystinuria in children, and Ehlers-Danlos in young adults. Patient presentations: Marfans - scoliosis, long fingers, and caved in chest wall in a tall teen; Homocystinuria - developmental delay, long fingers, and tall stature in a child; Ehlers-Danlos - recurrent bruising, hyper extensible skin, and joint hyperextensibility in a young adult.