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: Medicine
Omenn syndrome represents which of the following immunological condition? 
Select and explain. 
A. Human Leukocyte antigen (HLA) Class II Deficiency, B. HLA Class I Deficiency, C. Purine Metabolism Deficiency, D. Subset of T cell deficiency
D: Subset of T cell deficiency
Answer: D: Subset of T cell deficiency 
Explanation: Omenn syndrome consists of a subset of T cell deficiencies that present with early-onset erythroderma, alopecia, hepatosplenomegaly, and failure to thrive. This peculiar syndrome is due to the hypomorphic mutations in genes usually associated with SCID, i.e., RAG-1, RAG-2,. The patients are very fragile, requiring simultaneous anti-infective therapy, nutritional suppo, and immunosuppression. Ref: Harrisons Principles of Internal Medicine, 18th Edition, Page 2701.