Multifocal micronodular pneumocyte hyperplasia

Multifocal micronodular pneumocyte hyperplasia (MMPH) is a rare benign hamartomatous proliferation of type II pneumocytes and is mostly seen in association with tuberous sclerosis (TS). It can occur with or without concurrent lymphangiomyomatosis.

Radiographic features

CT chest

Seen as random faint but relatively well defined small (1-10 mm ^1,4) nodular lung parenchymal densities in patients with tuberous sclerosis. These tend to be diffusely scattered throughout the lung in a random distribution with regard to the secondary lobule ¹.

Treatment and prognosis

Unlike lymphangiomyomatosis, multifocal micronodular pneumocyte hyperplasia is not progressive and therefore treatment is not required ³.

History and etymology

It was first described by Popper et al. in 1991 ⁷.

Differential diagnosis

General imaging differential considerations include

• multiple atypical adenomatous hyperplasia (MAAH)

• early pulmonary Langerhans cell histiocytosis: prior to cyst formation

• minute hematogenous lung metastases

• miliary tuberculosis

• diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH): often has an association with mosaic attenuation pattern