Petechiae are caused by burst capilaries under the skin and are not usually raised bumps...they're like tiny bruises.
Purpura are slightly larger but still pretty small (under 1 cm in diameter).
An online search reveals a huge list of potential causes, including rickettsia, Rocky Mountain Spotted Fever, and a few borrelia strains...which leads me to believe that any tick-borne illness or coinfection could cause this type of rash.
Chronic Lyme Disease, Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut issues (dysmotility, non-specific inflammation), UCTD ("Secondary Lupus-Like Syndrome"), Osteoporosis, Pancytopenia, chronic malabsorption/malnutrition, etc.; G-Tube; Currently TPN-dependent.
Meds: Zofran, Pulmicort, IV Ceftazidime, Heparin (to flush PICC line), Claritin, Colloidal Silver (used topically), probiotics, homeopathy.