A young woman with recurrent pneumothorax, progressive exertional dyspnoea, and obstructive pulmonary function tests may have more than asthma or a primary spontaneous pneumothorax. Lymphangioleiomyomatosis (LAM) is a rare systemic, low-grade neoplastic disease in which abnormal LAM cells progressively infiltrate the lungs and lymphatic system. The resulting combination of diffuse cystic lung destruction, chylous fluid accumulation, and abdominal lesions—especially renal angiomyolipomas—creates a recognizable clinical pattern. Three decisions prevent the most consequential errors: do not diagnose LAM from a characteristic chest CT alone; recognize that a LAM-associated pneumothorax is a secondary pneumothorax with a high recurrence risk; and treat progressive disease with specialist-directed mTOR inhibition while remembering that sirolimus suppresses LAM rather than eradicating it. In Canada, sirolimus use for LAM is off-label, even though it is guideline-directed. Clinical trajectory check Link new findings to the underlying process and the compensatory response that is succeeding or failing. Reassess objective trends such as perfusion, oxygenation, mental status, pain pattern, labs, and response to time-limited interventions so the next action reflects improvement or deterioration rather than a memorized label. For NCLEX-RN (Canada), items...