Let m ≥ 2 be an integer. For any open domain Ω ⊂ R 2m , non-positive function ϕ ∈ C ∞ (Ω) such that ∆ m ϕ ≡ 0, and bounded sequence (V k ) ⊂ L ∞ (Ω) we prove the existence of a sequence of functions (u k ) ⊂ C 2m−1 (Ω) solving the Liouville equation of order 2m (−∆) m u k = V k e 2mu k in Ω, lim sup k→∞ Ω e 2mu k dx < ∞, and blowing up exactly on the set S ϕ := {x ∈ Ω : ϕ(x) = 0}, i.e. lim k→∞ u k (x) = +∞ for x ∈ S ϕ and lim k→∞ u k (x) = −∞ for x ∈ Ω \ S ϕ , thus showing that a result of Adimurthi, Robert and Struwe is sharp. We extend this result to the boundary of Ω and to the case Ω = R 2m . Several related problems remain open.