A 3-year-old male presents for the evaluation of pain and difficulty moving his right arm. He was seen in Urgent Care 3 days ago for an upper respiratory infection with fever and was prescribed an inhaler and a short course of steroids for wheezing, but there was no weakness noted.
He continued to be febrile and fussy. During breakfast this morning his mother noticed he was not picking up food with his right hand, but only using his left, and that he would sometimes use his left hand to move his right arm. His mother reports that he may have fallen onto an outstretched arm while playing the day before, but he didn’t seem to have hurt himself.
On physical examination, the child is mildly ill appearing and fussy. He has mild upper respiratory congestion, but normal breath sounds, and febrile to 101. His right arm hangs limp by his right side. He appears uncomfortable when it is manipulated, but there is no obvious injury. He is unable to give a high five, but is able to demonstrate a pinching movement with the fingers of that hand. Deep tendon reflexes are decreased in the affected arm, but sensation is normal.
What is the most likely diagnosis?
No one correctly guessed the diagnosis from the fall issue, which was single large-scale mitochondrial DNA deletion syndrome (SLSMDS), classically labeled as Pearson syndrome, the subject of this issue’s cover article.