major clinical manifestations of homocystinuria I
• Ectopia lentis (lens dislocated downward); hallmark finding (96%).
• Thromboembolism (most common cause of death); both arterial and venous.
• Mental deficiency, seizures, ischemic strokes.
• Marfanoid habitus but without joint laxity.
Musculoskeletal findings include tallness, arachnodactyly (dolichostenomelia), pes cavus, genu valgum, and chest wall (pectus) and spinal deformity. Osteoporosis (generalized) and tight joints occur. Spinal osteoporosis occurs in up to 64% of affected individuals by the age of 15 years. Spinal disease is prominent and is usually a combination of osteoporotic fractures, degenerative disc/joint disease, and scoliosis.
Pearl: Rule out homocystinuria in patients with a Marfanoid habitus who have stiff joints and mental deficiency.
