Rotator Cuff Tendinitis: This condition is a common cause of shoulder pain, especially with repetitive movement. The rotator cuff is a group of muscles and tendons surrounding the shoulder joint, and inflammation or strain in this area can lead to pain and potentially radiate to the arm, causing parasthesia.

Thoracic Outlet Syndrome (TOS): This condition involves compression, injury, or irritation of the nerves and/or blood vessels (arteries and veins) in the thoracic outlet area, which lies between your collarbone (clavicle) and first rib. This can cause pain in the shoulder and arm, as well as parasthesia.
Cervical Radiculopathy: This refers to damage or irritation of the nerve roots in the cervical spine, which can cause pain, numbness, and tingling (parasthesia) in the shoulder and arm. Repetitive movements can exacerbate the condition.
Bursitis: Inflammation of the bursae, fluid-filled sacs that cushion bones, tendons, and muscles near joints, can cause pain and stiffness, especially with movement. While less likely to cause parasthesia directly, severe cases could potentially irritate nearby nerves.

Myocardial Infarction (MI): Although less common, shoulder pain can be a referred pain from a heart attack, especially in women. The presence of parasthesia could be indicative of a more complex cardiac issue.
Pulmonary Embolism: While typically presenting with respiratory symptoms, in rare cases, a pulmonary embolism can cause referred pain to the shoulder and arm, especially if the embolism affects blood flow to areas that also innervate these regions.
Spinal Cord Injury or Compression: Any condition that compresses or injures the spinal cord can cause a wide range of neurological symptoms, including pain, weakness, and parasthesia in the arms. This would be a medical emergency.

Pancoast Tumor: A rare type of lung cancer that grows in the upper part of the lung and can invade nearby tissues, including nerves, leading to shoulder and arm pain, as well as parasthesia.
Brachial Plexitis (Neuralgic Amyotrophy): An inflammatory condition that affects the nerves of the brachial plexus, causing severe pain, usually in one arm, followed by weakness or paralysis. It's a rare condition but should be considered in cases of unexplained arm pain and parasthesia.
Complex Regional Pain Syndrome (CRPS): A chronic pain condition characterized by severe, burning pain at the site of an injury, which can be out of proportion to the severity of the injury. It can also cause parasthesia and is typically confined to one limb.