Niemann-Pick Type B: A Rare Cause of Interstitial Lung Disease

Abstract

Niemann-Pick disease (NPD) is a rare lysosomal storage disease (LSD) with multisystemic involvement. The disease is heterogeneous and classified into three subtypes: type A and B result from deficient acid sphingomyelinase activity and leads to the accumulation of sphingomyelin and type C is a genetically different disease resulting from defective intracellular trafficking of cholesterol with accumulation of glycosphingolipids. Type A is generally a neurodegenerative disease and is fatal in infancy. Type B is a less severe form characterized by pulmonary involvement, hepatosplenomegaly, hyperlipidemia and most patients live into adulthood. In type C, clinical presentation is dominated with neurological involvement. Pulmonary involvement occurs in all three types of Niemann-Pick but most frequently in type B. Clinical manifestations range from a lack of symptoms to respiratory failure, and respiratory symptoms are usually mild with recurrent cough, dyspnoea on exertion and recurrent respiratory infections. Interstitial lung disease (ILD) is the most prominent feature with slow progression, characterized by worsening pulmonary function tests. In recent years, enzyme replacement therapy has shown promising results in clinical trials, such as improvement in organomegaly and pulmonary involvement with the potential to improve patients' lives. We present three cases of NPD with pulmonary involvement, each exhibiting a different pattern of ILD and evaluate therapeutic options.

Keywords: enzyme replacement therapy; interstitial pulmonary disease; lysosomal storage disorder; niemann pick type b; respiratory.

Figure 1. Thoracic CT scan showing ground-glass opacities (black arrow) with interlobular septal thickening (white arrows).

Figure 2. Chest radiography shows reticular infiltrates (white arrows).

Figure 3. CT scan showing bilateral lower lobes ground glass opacities associated with intermixed interlobular lines in lower lobes (white arrows).

Figure 4. Emphysema lesions in upper lobes (white arrow) and lower lobes with bronchiectasis (red arrow).

Figure 5. CT scan showing hepatosplenomegaly.

Figure 6. Discrete interlobular septal thickening (black arrow) and subpleural calcified micronodules (white arrow).