Thymus hyperplasia, differential diagnosis in the wheezing infant.

Thymus hyperplasia is not a rare condition in infancy, but it is generally considered not to cause any symptoms. We present here a series of 11 children seen at the National Institute of Pediatrics (NIP), Mexico-city, that do have respiratory symptoms secondary to the enlarged gland. Age of onset of the symptoms was median at birth, with age of first visit to the NIP of 6 months. Symptoms were respiratory crisis and various respiratory complaints. Five underwent thoracotomy and resection of the right pulmonary lobe was necessary in one, because of irreversible changes in the lung tissue due to chronic compression. In another patient thymic lobectomy was executed because extrinsic compression of the right upper bronchus resulted in recurrent atelectasia. The five biopsies taken during the intervention showed normal or hyperplastic or involutive thymic tissue without signs of malignancy. The evolution was positive in all the patients. In conclusion thymic hyperplasia must be taken into account in the evaluation of an infant with respiratory symptoms.