Is it possible to have a smoldering myodesplastic syndrome or mastocytosis with few major symptoms that goes unnoticed or undiagnosed for a few years to then suddenly get worse with extreme symptoms over just a few days making you extremely sick?

A smoldering bone marrow problem should not cause any symptom. Mastocytosis can become symptomatic even in minutes not days.

Any thing can happen, however, rare diagnoses are rarely correct. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV vaccine. Wish you good health! Safe sex: https://www.hopkinsmedicine.org/health/wellness-and-prevention/safer-sex-guidelines