Multifocal micronodular pneumocyte hyperplasia (MMPH) in a patient with tuberous sclerosis-evidence for long term stability

Multifocal micronodular pneumocyte hyperplasia (MMPH) is rare entity seen mostly in patients with the tuberous sclerosis complex (TSC). We present the case of a 50 year old woman with TSC (confirmed TSC2 mutation) found to have multiple ground glass opacities with an upper lobe predominance on a screening chest CT. No abnormalities were detected in other viscera. A thoracoscopic lung biopsy obtained from right upper lobe confirmed the diagnosis of MMPH. There were no lesions suggestive of lymphangioleiomyomatosis (LAM) either on the chest CT or lung biopsy. A repeat CT chest obtained on follow up 9 years after initial diagnosis continued to show stability of all MMPH ground glass lesions. This case highlights the distinct patterns of lung involvement in TSC, with MMPH having a benign and stable nature as compared to LAM which is often relentlessly progressive with associated lung function decline.