However, there are few data on tracking disease response in patients with rarer retinoid resistant subtypes of APL, characterized by PLZF-RARA and STAT5b-RARA.     ///    "Despite their rarity (<1% of APL) we identified 6 cases (PLZF-RARA, n?=?5. "    ///    Serial samples were available from two PLZF-RARA APL patients. 