Disorders causing a delay in the acquisition of or loss of milestones fit under this very broad category. Some disorders cause a plateauing of the individuals acquisition of developmental skills. This group of disorders can cause global developmental delays or they could affect various domains of development to different degrees causing speech/language delays, motor delays (gross and/or fine motor) or cognitive delays.
Individuals with developmental delays often require a comprehensive evaluation and a multidisciplinary team overseeing their care. They require a detailed developmental assessment by physical, occupational and speech therapists as well as their neurologist and neuropsychologist. Other tests that may be required (depending on their unique situations) could include a brain MRI, EEG and laboratory testing (possibly including genetic testing).
Other than supportive treatment, diagnosis or symptom specific treatments may also be recommended.