Hydroxychloroquine in Pediatric ILD With Genetic Surfactant Dysfunction Disorders: Cross-control, Prospective Study

Children Interstitial lung disease (chILD) is a heterogeneous group of rare respiratory disorders of known and unknown etiologies that are mostly chronic and associated with high morbidity and mortality. ILD are characterized by inflammatory and fibrotic changes of the lung parenchyma structure that typically result in the presence of diffuse infiltrates on lung imaging, and abnormal pulmonary function tests with evidence of a restrictive ventilatory defect and/or impaired gas exchange.

Genetic factors are important contributors to chILD. Genetic variations have been mainly described in genes encoding (or interacting with) the surfactant proteins (SP): SP-C (SFTPC) and the ATP-binding cassette-family A-member 3 (ABCA3) (ABCA3), and less frequently in the genes encoding NKX homeobox 2 (NKX2)-1 (NKX2-1), SP-B (SFTPB), SP-A (SFTPA) and other genes.

To date, the therapeutic managements of such chILD remain limited and are mainly based of the use of corticosteroids, however, their efficacy is highly variable. An alternative approach to treatment was originally described by Tooley who reported a good response to treatment with chloroquine in a girl with ILD, and several case reports have shown a positive response to hydroxychloroquine(HCQ) alone or in combination with systemic steroids of the children with ILD.

The exact mechanism of action of HCQ is unknown, but is probably due to its anti-inflammatory properties, HCQ have lysosomal activities such as diminished vesicle fusion, diminished exocytosis, decreased digestive efficiency of phagolysosomes and reversible "lysosomal storage disease. This may be the mechanism by which HCQ tend to help in chILD, especially in those cases related to surfactant protein deficiency. SP-B and SP-C are synthesized in the endoplasmic reticulum (ER) of alveolar type II cells as large precursor proteins, are cleaved by proteolytic enzymes and transported through Golgi apparatus to multivesicular bodies that fuse with lamellar bodies. In chILD related to SP-C gene mutations, there is misfolding of proSP-C that accumulates within ER and Golgi apparatus in alveolar type II cells, resulting in cellular injury and apoptosis. Treatment with HCQ may interfere with this accumulation of pro-surfactant proteins within alveolar cells.

The investigators propose to study the efficacy and safety of the therapy with HCQ for children with chILD suffered with genetic mutations, and its long-term effects. Through this study the investigators hope to confirm the benefits of HCQ in the treatment of this rare disease.