  We report the detection of a large amplitude MIR outburst in the white dwarf
(WD) 0145+234 in the NEOWISE Survey data. The source had a stable MIR flux
before 2018, and was brightened by about 1.0 magnitude in the W1 and W2 bands
within half a year and has been continuously brightening since then. No
significant variations are found in the optical photometry data during the same
period. This suggests that this MIR outburst is caused by recent replenishing
or redistribution of dust, rather than intrinsic variations of the WD. SED
modeling of 0145+234 suggests that there was already a dust disk around the WD
in the quiescent state, and both of the temperature and surface area of the
disk evolved rapidly since the outburst. The dust temperature was about 1770K
in the initial rising phase, close to the sublimation temperature of silicate
grains, and gradually cooled down to around 1150K, while the surface area
increased by a factor of about 6 during the same period. The inferred closest
distance of dust to the WD is within the tidal disruption radius of a
gravitationally bounded asteroid. We estimated the dust mass to be between
$3\times10^{15}$ to $3\times10^{17}$ $\rho/(1 \mathrm g~cm^{-3})$ kg for
silicate grains of a power-law size distribution with a high cutoff size from
0.1 to 1000 microns. We interpret this as a possible tidal breakup of an
exo-asteroid by the WD. Further follow-up observations of this rare event may
provide insights on the origin of dust disk and metal pollution in some white
dwarfs.
