<prompt> Answer this question truthfullyWhat is the rapid diagnosis for a tall, fair-skinned and thin girl with hyperextensive skin and joint hyperlaxity who develops sudden-onset weakness and also has developmental delay?  <response>: <reason> The rapid diagnosis for a tall, fair-skinned and thin girl with hyperextensive skin and joint hyperlaxity who develops sudden-onset weakness and also has developmental delay is Homocystinuria with marfanoid body habitus. 