This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
All of the following conditions have autosomal dominant inheritance except - 
Select and explain. 
A. Fabry disease, B. Marfan's syndrome, C. Osteogenesis imperfecta, D. Ehlers Danlos syndrome
A: Fabry disease
Answer: A: Fabry disease 
Explanation: Ans. is 'a' i.e., Fabry's disease Autosomal dominant disorders o Normally a gene pair has two alleles. o When one allele becomes abnormal due to mutation it is called heterozygous state. o When both the alleles become abnormal due to mutation it is called homozygous state. o Autosomal dominant disorders are manifested in heterozygous state, i.e. only if one allel is abnormal the disease will be manifested.