Viral Pharyngitis: This is the most common cause of sore throat in adolescents, and abdominal pain can sometimes accompany viral infections due to systemic symptoms or referred pain.

Strep Pharyngitis: Although less common than viral pharyngitis, streptococcal infections can cause severe sore throat and may be accompanied by abdominal pain, especially if the infection leads to systemic symptoms.
Gastroesophageal Reflux Disease (GERD): GERD can cause both abdominal pain and sore throat due to acid reflux irritating the throat.
Viral Gastroenteritis: This condition can cause abdominal pain and, in some cases, a sore throat if the virus affects the upper respiratory tract as well.

Appendicitis: Although abdominal pain is a key symptom, a sore throat could be an unrelated coincidental finding. Appendicitis is a surgical emergency and must be considered in any case of abdominal pain.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can present with abdominal pain and sometimes extraintestinal symptoms, including sore throat due to oral ulcers or systemic inflammation.
Kawasaki Disease: This rare condition can present with fever, abdominal pain, and sore throat among other symptoms, and is a medical emergency due to the risk of cardiac complications.

Lemierre's Syndrome: A rare condition characterized by a bacterial infection of the throat (usually by Fusobacterium necrophorum) that can lead to sepsis and abdominal pain due to metastatic infection or thrombophlebitis.
Systemic Lupus Erythematosus (SLE): A chronic autoimmune disease that can present with a wide range of symptoms, including sore throat and abdominal pain, due to its systemic nature.
Henoch-Schönlein Purpura (HSP): A form of vasculitis that can cause abdominal pain and sometimes sore throat, along with the characteristic purpuric rash.