Adenosine deaminase (ADA) enzyme is crucial for the immune system to function. Hence, its deficiency results in the dysfunction of immune system.

$\bullet$ Hyposecretion of hormones of the adrenal cortex causes Addison's disease.

$\bullet$ Parkinson's disease is a long-term degenerative disorder of the central nervous system.

$\bullet$ Disorders which affect GIT & associated glands are called digestive disorders.