TRIGGERING PHEOCHROMOCYTOMA MULTISYSTEM CRISIS; THROMBOCYTOPENIA; This spontaneous report was received from literature: Johnson and Johnson COVID-19 Vaccination Triggering Pheochromocytoma Multisystem Crisis. Cureus. 22-SEP-2021; 13/9. This report concerned a 63 year old Caucasian male of unspecified ethnic origin. The objective of this study was to describe Johnson and Johnson COVID-19 Vaccination Triggering Pheochromocytoma Multisystem Crisis. The patient's height, and weight were not reported. The patient's concurrent conditions included: daily marijuana use. Patient had no symptoms prior to this and no significant past medical history.  The patient received Covid-19 vaccine ad26.cov2.s (suspension for injection, route of admin not reported, batch number: unknown, expiry: unknown) dose was not reported, 1 total was administered on 07-MAY-2021 for prophylactic vaccination. The batch number was not reported and has been requested. No concomitant medications were reported.  One day later after vaccination, on 08-MAY-2021, patient developed intractable nausea, vomiting, dyspnea, watery diarrhea, chills, sweats, and heavy chest pain. On an unspecified date in MAY-2021, Patient underwent emergency department (ED) and hospitalized, the patient was tachycardic at 120 {beats}/min, hypoxic with oxygen 88 percent on room air, brain natriuretic peptide (BNP) 3421 pg/ml, elevated troponins at 1.29 ng/ml, procalcitonin 25 ng/ml, lactic acid 5.0 mmol/L, white blood cells 19 K/UL, thrombocytopenia at 101 K/UL, and creatinine 1.91 mg/dL. Initial chest X-ray showed bilateral airspace opacities consistent with atypical pneumonia. The patient was intubated because he was in severe respiratory distress with use of accessory muscles and decreased oxygen saturation. Patient was put on ventilator (ventilator settings are- Fraction of inspired oxygen (FiO2): 100 percent, Respiratory rate (RR): 16 breaths per minute, Positive end-expiratory pressure (PEEP): 10 cm H20). Echo showed an ejection fraction (EF) of 25 percent with global hypokinesis and grade 3 diastolic dysfunction. A right heart catheterization was performed, showing severe pulmonary hypertension. An intra-aortic balloon pump was inserted, but his condition continued to decline, so a left-sided Impella device was placed and milrinone and norepinephrine were started. The patient was tested for infectious causes and all were negative including two negative COVID-19 results, viral panel, blood cultures, urine cultures, sputum cultures, and urine legionella. A chest X-ray shows diffuse interstitial and patchy alveolar opacities. Throughout his nine-day hospital stay, patient continued to have rapid cyclical fluctuations of hypertension (260s/130s) and hypotension (40s/20s), persistent fevers up to 40.2 degree celcius, and acute respiratory distress syndrome (ARDS)-like picture. His other problems included acute tubular necrosis (ATN) from an acute kidney injury (AKI), hypernatremia, arterial catheter-associated thrombosis in mid left radial artery leading to gangrene of left 1st and 2nd digits, non-ST-elevation myocardial infarction (NSTEMI) with cardiogenic shock (on 10-MAY-2021, EF was 55 percent with no diastolic dysfunction), subclinical hyperthyroidism, and electroencephalogram (EEG) showed diffuse slowing, with no epileptiform activity. On 15-MAY-2021, Echo showed EF of 43 percent with mild global hypokinesis. Neuroendocrine crisis was suspected, and the patient was worked up for pheochromocytoma and carcinoid. Laboratory data included: Metanephrine plasma was 31.1 nmol/L (Reference range: less than 0.5) , Normetanephrine plasma was 8.9 nmol/L (Reference range: less than 0.9), Urine Vanillylmandelic acid was 153.9 mg/day (Reference range: 1.8 - 6.7), 24-hour urine total metanephrines was 54,391 ug/day (Reference range: 140 - 785), 24-hour urine creatinine was 1.1 gm/24h (Reference range: 1.0 - 2.0), 24-hour urine metanephrines was 36,144 ug/day (Reference range: 52 - 341), 24-hour urine normetanephrines was 18,247 ug/day (Reference range: 88 - 444), and 24-hour urine 5-Hydroxyindoleacetic acid was 5.0 mg/24h (Reference range: 3-10). The retroperitoneal ultrasound showed 7.0 6.2 7 cm heterogenic mass in right adrenal gland. Due to patient's labile blood pressure measurements, he was on and off of vasopressors (such as norepinephrine) and anti-hypertensive medications (nitroglycerin). The first step in the diagnosis of pheochromocytoma was done that was discontinuation of medications that might interfere with metanephrine levels such as norepinephrine. The results of significantly elevated 24-hour urine fractionated metanephrines and catecholamines or elevated fractionated plasma metanephrines confirmed the diagnosis of pheochromocytoma. Imaging with CT (Computerised tomogram) or MRI (Magnetic resonance imaging) should be done to localize the tumor, but the patient was not stable enough for these imaging tests and thus ultrasound was performed. There were no previous imaging studies on record for this patient or a family history that could explain the etiology of his tumor.  On 21-MAY-2021, the patient was transferred to the another hospital for mass resection. A computerised tomogram (CT) was performed the same day to confirm the ultrasound finding of a 7 cm heterogeneous right adrenal mass. The patient continued to suffer from acute hypoxemic respiratory failure and a tracheostomy was performed on 07-JUN-2021 due to prolonged intubation. His stay at hospital was also complicated by episodes of non-sustained ventricular tachycardia (NSVT) that responded well to synchronized cardioversion. He was also placed on amiodarone. On 18-JUN-2021, an open right adrenalectomy was performed. On 22-JUN-2021, repeat plasma metanephrine was found to be less than 0.2 nmol/L and plasma normetanephrine was 0.9 nmol/L. An echo performed on same day, revealed a left ventricular EF of 63 percent, normal overall ventricular systolic function, normal overall right ventricular systolic function, and no significant valvular dysfunction. On 24-JUN-2021, multiple upper and lower extremity deep vein thromboses (DVTs) were found. The patient was treated with blood thinners and stabilized for transfer to inpatient rehabilitation on 02-JUL-2021. The patient was hospitalized for unspecified days and then discharged on 12-JUL-2021. He was continued outpatient therapy and now able to walk on his own and perform all of his activities of daily living independently. Patient would be on follow up with endocrine genetics for the etiology of his pheochromocytoma, cardiology, and physical medicine and rehabilitation. He would be continuing amiodarone for NSVT and rivaroxaban for the DVTs until the end of SEP-2021. The patient had been doing very well overall. The action taken with Covid-19 vaccine ad26.cov2.s was not applicable. The patient was recovering from triggering pheochromocytoma multisystem crisis (intractable nausea, vomiting, sweats, persistent high fevers, heavy chest pain, multiple upper and lower extremity deep vein thromboses, watery diarrhea, chills, hypernatremia, acute hypoxemic respiratory failure/acute respiratory distress syndrome/dyspnea, arterial catheter associated thrombosis in mid left radial artery leading to gangrene, severe pulmonary hypertension, acute kidney injury, subclinical hyperthyroidism, cardiomyopathy, labile blood pressure, rapid cyclical fluctuations of hypertension and hypotension, acute tubular necrosis (ATN), non-ST-elevation myocardial infarction (NSTEMI), neuroendocrine crisis, mild global hypokinesis, cardiogenic shock, diastolic dysfunction, non-sustained ventricular tachycardia (NSVT)) and thrombocytopenia. The author emphasized on Pheochromocytomas that are rare and benign tumors. Most are asymptomatic and rarely present with multisystem organ dysfunction and labile blood pressures when symptoms are present. A pheochromocytoma crisis in previously asymptomatic patients may be triggered by certain medications (such as rocuronium and corticosteroids) or as in our patient, the J&J COVID-19 vaccine. Further studies would be needed to investigate how exactly these medications and the J&J COVID-19 vaccine cause a pheochromocytoma crisis. Diagnosis could be confirmed with significant elevations in biochemical tests and abdominal imaging could localize the tumor for eventual resection. Some pheochromocytomas did not present with classic symptoms of paroxysmal hypertension, episodic headache, sweating, and tachycardia; thus, it was prudent to remain suspicious when patients present with sudden symptoms of multiorgan dysfunction, labile blood pressures, and hyperthermia suggesting the triggering of a previously dormant pheochromocytoma. This report was serious (Hospitalization Caused / Prolonged, and Life Threatening).; Sender's Comments: V0: 20211060859-COVID-19 VACCINE AD26.COV2.S- Triggering pheochromocytoma multisystem crisis, Thrombocytopenia. These events are considered unassessable. The events have a compatible/suggestive temporal relationship, are unlabeled, and have unknown scientific plausibility. There is no information on any other factors potentially associated with the events.