The cause of pseudoclass III malocclusion is:
Functional class III or Pseudo class III
This condition requires special mention because treatment of this class of malocclusion is entirely different from the true class III situation. The differentiating feature of this condition is that the dental occlusion is class III in maximum intercuspation or habitual occlusion, while it is actually class I in centric occlusion. Here the disturbance is a functional one, where as a result of dental interference, the mandible is deviated anteriorly to achieve a ‘bite of convenience’. Thus, a static evaluation will give a class III reading, but functional examination at postural rest and at first dental contact shows that the mandible is closing in a normal class I way.
Ref:Orthodontics: Diagnosis and Management of Malocclusion and Dentofacial Deformities
THIRD EDITION Om P. Kharbanda  Pg- e328
Developmental deficiency
Increased mandibular growth
Functional abnormality
Hormonal disturbance