Which condition is classified as a congenital disorder?

The condition classified as a congenital disorder is onychatrophia. This condition involves a deformity or deficiency in the nails that is present from birth. Congenital disorders are those that occur during fetal development and manifest at or shortly after birth, affecting the structure and function of various body parts.

Boils, eczema, and folliculitis are all conditions that arise due to external factors or reactions rather than being present at birth. Boils are caused by bacterial infections, eczema is an inflammatory skin condition that can be triggered by genetics and environmental factors, and folliculitis is an infection of the hair follicles, often due to irritation or bacterial infection. Therefore, onychatrophia is the only condition listed that fits the definition of a congenital disorder, making it the correct choice.