  Primordial black holes can represent all or most of the dark matter in the
window $10^{17}-10^{22}\,$g. Here we present an extension of the constraints on
PBHs of masses $10^{13}-10^{18}\,$g arising from the isotropic diffuse gamma
ray background. Primordial black holes evaporate by emitting Hawking radiation
that should not exceed the observed background. Generalizing from monochromatic
distributions of Schwarzschild black holes to extended mass functions of Kerr
rotating black holes, we show that the lower part of this mass window can be
closed for near-extremal black holes.
