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
Patients with axonal neuropathy, unexplained abdominal pain along with history of psychiatric illness may be suffering from: 
Select and explain. 
A. Porphyria, B. PNH, C. Arsenic toxicity, D. Hypothyroidism
A: Porphyria
Answer: A: Porphyria 
Explanation: In patients with an axonal GBS, unexplained abdominal pain, psychiatric illness should be screened for porphyria. MUST KNOW: In GBS in CSF study if cells are present should suspect HIV infection, Lyme disease, sarcoidosis, or lymphomatous or leukemic infiltration of nerve roots. PNH patients may present with abdominal pain but peripheral neuropathy and psychiatric illness are not seen. Ref: Harrison, Edition-18, Page-3450