Differential Diagnosis for Intermittent Flushing and Severe Fatigue
Single Most Likely Diagnosis
- Carcinoid Syndrome: This condition is characterized by intermittent flushing, diarrhea, wheezing, and heart valve abnormalities, often associated with a neuroendocrine tumor. The mild elevation of chromogranin supports this diagnosis, although the normal F18 PET scan may indicate a small or slow-growing tumor.
Other Likely Diagnoses
- Mastocytosis: A condition where mast cells accumulate in various tissues, leading to symptoms like flushing, fatigue, and gastrointestinal issues. The daily occurrence of flushing and severe fatigue could be indicative of mastocytosis, especially if other symptoms like hives or itching are present.
- Pheochromocytoma: Although less likely given the normal F18 PET scan, pheochromocytoma can cause episodic flushing, fatigue, and other symptoms due to catecholamine surges. The mild elevation of chromogranin could also support this diagnosis.
- Medullary Thyroid Carcinoma: This rare thyroid cancer can produce flushing and diarrhea due to the secretion of calcitonin and other peptides. The mild elevation of chromogranin could be relevant, but specific markers like calcitonin levels would be more diagnostic.
Do Not Miss Diagnoses
- Neuroendocrine Tumors (other than Carcinoid): Including pancreatic neuroendocrine tumors or other gastroenteropancreatic neuroendocrine tumors that could secrete various peptides leading to flushing and fatigue. The mild elevation of chromogranin is a clue, and missing such a diagnosis could lead to delayed treatment of a potentially serious condition.
- Systemic Mast Cell Activation Syndrome: Similar to mastocytosis but without the accumulation of mast cells. It can present with similar symptoms and requires a high index of suspicion for diagnosis.
Rare Diagnoses
- Harlequin Syndrome: A rare condition characterized by asymmetric flushing and sweating, typically affecting one side of the face. It's less likely given the description of intermittent flushing occurring daily, but it could be considered if the flushing pattern is unusual.
- Erythromelalgia: A disorder that causes burning pain, heat, and redness in the hands and feet, sometimes accompanied by flushing. It's a less likely cause of the described symptoms but could be considered if pain in the extremities is also present.