Ventilation/Perfusion scan aids in the diagnosis of diabetes mellitus induced trepopnea due to isolated right phrenic nerve palsy

Dyspnea can rarely be due to diabetes mellitus induced neuropathy. The term “trepopnea’ is sparingly used in clinical practice and refers to dyspnea on assuming a particular lateral decubitus position Trepopnea is rarely described in association with unilateral diaphragmatic paralysis, which in itself is an uncommon cause of respiratory distress. We report a 27-year-old diabetic female who presented with sudden onset of dyspnea. On close interrogation, patient complained of dyspnea that was exaggerated while lying on the left side (left lateral decubitus position). A fluoroscopic sniff test showed a paradoxically moving right diaphragm confirming the diagnosis of unilateral diaphragmatic paralysis attributed to diabetes induced isolated phrenic nerve palsy. This case highlights the importance of ventilation — perfusion imaging in non-pulmonary etiologies and also attaches importance in recognizing trepopnea as an early clinical symptom of diaphragmatic paralysis. This case illustrates that diabetic neuropathy due to isolated phrenic nerve palsy can occur in the absence of peripheral neuropathy and that glycemic control is unrelated to the manifestation or severity of this disease.