osis ▁of ▁an ▁imm un ode fic iency ▁include ▁rec urrent ▁or ▁persistent ▁in fe ctions ▁or ▁development al ▁delay ▁as ▁a ▁result ▁of ▁in fection . ▁Part icular ▁organ ▁problems ▁( e . g . ▁dise ases ▁involving ▁the ▁skin , ▁heart , ▁fa cial ▁development ▁and ▁ske let al ▁system ) ▁may ▁be ▁present ▁in ▁certain ▁conditions . ▁O thers ▁pre dis pose ▁to ▁auto imm une ▁disease , ▁where ▁the ▁imm une ▁system ▁attacks ▁the ▁body ' s ▁own ▁t issues , ▁or ▁tum ours ▁( s ometimes ▁specific ▁forms ▁of ▁cancer , ▁such ▁as ▁l ym ph oma ). ▁The ▁nature ▁of ▁the ▁in fe ctions , ▁as ▁well ▁as ▁the ▁additional ▁features , ▁may ▁provide ▁cl ues ▁as ▁to ▁the ▁exact ▁nature ▁of ▁the ▁imm une ▁defect . ▁ ▁C aus es ▁By ▁definition , ▁primary ▁imm une ▁def ic ien cies ▁are ▁due ▁to ▁gen etic ▁causes . ▁They ▁may ▁result ▁from ▁a ▁single ▁gen etic ▁defect , ▁but ▁most ▁are ▁mult ifact orial . ▁ ▁They ▁may ▁be ▁caused ▁by ▁re cess ive ▁or ▁dominant ▁inheritance . ▁ ▁Some ▁are ▁lat ent , ▁and ▁require ▁a ▁certain ▁environmental ▁trigger ▁to ▁become ▁manifest , ▁like ▁the ▁presence ▁in ▁the ▁environment ▁of ▁a ▁re active ▁aller gen . ▁ ▁Other ▁problems ▁become ▁apparent ▁due ▁to ▁ag ing ▁of ▁bod ily ▁and ▁cell ular ▁maintenance ▁processes . ▁ ▁Di agn osis ▁The ▁basic ▁tests ▁performed ▁when ▁an ▁imm un ode fic iency ▁is ▁sus pected ▁should ▁include ▁a ▁full