Differential Diagnosis for the Patient's Symptoms

The patient presents with a complex array of symptoms, including exocrine pancreatic insufficiency (EPI), insomnia, skin rashes, and other systemic issues. The following differential diagnosis is organized into categories to help identify the ultimate cause of the patient's symptoms.

• Single Most Likely Diagnosis
  • Autoimmune Disorder: Given the patient's history of EPI, response to PERT and supplementation, improvement with quercetin (an anti-inflammatory), and various systemic symptoms such as skin rashes and knee pain, an autoimmune disorder is a strong consideration. Conditions like autoimmune pancreatitis or a broader autoimmune syndrome could explain the multifaceted presentation.
• Other Likely Diagnoses
  • Small Intestine Bacterial Overgrowth (SIBO): The patient's improvement with psyllium husk powder and the specific pattern of fecal fat tests could suggest malabsorption issues, potentially related to SIBO, which is known to cause insomnia and gastrointestinal symptoms.
  • Mast Cell Activation Syndrome (MCAS): The patient's symptoms of flushing, warmth without sweating, and improvement with ibuprofen and curcumin (both of which have anti-inflammatory properties) could be indicative of MCAS. The atypical rashes and reactions to certain supplements also support this diagnosis.
  • Inflammatory Bowel Disease (IBD): Although calprotectin and other inflammatory markers are normal, the patient's history of mysterious health issues, including vomiting and food allergies as a child, and current symptoms like insomnia and skin rashes, could still suggest a form of IBD, particularly if it's in a quiescent phase or not fully active.
• Do Not Miss Diagnoses
  • Lymphoma: Given the patient's history of mysterious health issues, including childhood epilepsy and current systemic symptoms, lymphoma should be considered, especially with the incidental finding of lung nodules. Lymphoma can cause a wide range of systemic symptoms, including insomnia and skin manifestations.
  • Neuroendocrine Tumors: These tumors can cause a variety of systemic symptoms, including flushing, warmth, and gastrointestinal issues, due to the secretion of various hormones. The patient's symptoms of waking with a feeling of warmth and the improvement with certain medications could suggest this diagnosis.
• Rare Diagnoses
  • Eosinophilic Gastroenteritis: Although eosinophil levels have been variable and not consistently elevated, and other specific markers like EPX are normal, this condition could still be considered given the patient's history of food allergies and atypical gastrointestinal symptoms.
  • Whipple's Disease: A rare, systemic bacterial infection that can cause malabsorption, weight loss, and a variety of other systemic symptoms, including skin rashes and joint pain. The patient's response to certain supplements and improvement in knee pain with quercetin might hint at an underlying infectious or inflammatory process, although this is less likely given the normal diagnostic tests for parasites and infections.

Each of these diagnoses offers a potential explanation for the patient's complex presentation, and further investigation, including specific diagnostic tests and potentially a trial of treatments, would be necessary to determine the underlying cause of the symptoms.