Can a lightning strike lead to structural damages of the fuselage and eventually cause decompression?
Decompression is a tricky thing.  The aircraft is already quite "leaky" and without a steady flow of pressurized air from the engine bleed air (or compressors, in the case of the 787) the altitude in the cabin will rise slowly. There is a pressure controlled outflow valve in the back of the aircraft that is usually about 10-20cm square. The pressurization system stuffs air in constantly, and the outflow valve opens and closes to keep the interior pressure at the correct altitude.  Any hole smaller than the amount of air the pressurization system can pump in will just be handled by the outflow valve closing somewhat.  Depressurization due to structural failure is fairly rare.  Most recent would be Southwest 1380, where an uncontained engine failure broke a window.  

I have not heard of a lightning strike even piercing the aircraft fuselage in modern civilian aircraft, much less in the cabin area.  There are a few cases I have heard of it happening to military aircraft, and in those the hole was fairly small (about 2-5cm in diameter).  Aircraft are regularly hit by lightning, and extensive testing is done to simulate lightning strikes before an aircraft can be certified.