Hydroxychloroquine (HCQ) in Pediatric Interstitial Lung Disease (ILD)

Inclusion criteria: 1. Patients should be clinically stable during baseline (between Visit 1 and 2) for inclusion into the study 1. To determine this, attending physicians can use SpO2 in room air for patients on room air or on O2-supplement; the absolute difference on SpO2 is expected not to be ≥ 5% between Visit 1 and 2. For patients on respiratory support, the summary key parameters should not change ≥ 20% between Visit 1 and 2 and 2. No major changes in other medications between Visit 1 and 2 2. Mature newborn ≥ 37 weeks of gestation, age ≥ 3 wks and \<2y or Infants and children (≥2y and \< 18y) or Adults (≥18 and ≤30y) or Previously preterm (≤ 37 weeks of gestation) babies or children and adults of all ages if chILD genetically diagnosed (see inclusion criterion 3.) 3. Diagnosis of chronic (≥ 3 wks of duration) diffuse parenchymal lung disease (DPLD = chILD), defined in at least one of the following ways: 1. chILD genetically diagnosed surfactant dysfunction disorders including patients with mutations in SFTPC, SFTPB, ABCA3, TTF1 (Nkx2-1), further extremely rare entities with specific mutations, for example in TBX4, NPC2, NPC1, NPB, COPA, LRBA and other genes. In this case, also previously preterm (≤ 37 weeks of gestation) babies or children and adults of all ages can be included into the study. 2. chILD histologically diagnosed * Chronic pneumonitis of infancy (CPI) * Desquamative interstitial pneumonia (DIP) * Lipoid pneumonitis / Cholesterol pneumonia * Nonspecific interstitial pneumonia (NSIP) * PAP after the exclusion of mutations in GMCSF-Ra/b and GMCSF autoantibodies\* * Usual interstitial pneumonia (UIP) * Follicular bronchitis/bronchiolitis/Lymphocytic interstitial pneumonia (LIP) * Storage disease with primary pulmonary involvement (e.g. Niemann Pick) * Hermansky-Pudlak Syndrome * Idiopathic pulmonary haemorrhage (haemosiderosis)\* * Other histology diagnosing chILD, in particular combination of the above pattern, but not exclusively 4. Start block: no HCQ treatment in the last 12 weeks Stop block: stable HCQ treatment for at least the last 12 weeks 5. Ability of subject or/and legal representatives to understand character and individual consequences of clinical trial. 6. Signed and dated informed consent of the subject (if subject has the ability) and the representatives (of underaged children) must be available before start of any specific trial procedures. (\*may be diagnosed in the absence of a lung biopsy by characteristic lung lavage cytology (PAS stain, Fe stain), CT pattern or autoantibodies (gliadin, endomysium; cANCA) and clinical course.) Exclusion criteria: Subjects presenting with any of the following criteria will not be included in the trial: * chILD primarily related to developmental disorders * chILD primarily related to growth abnormalities reflecting deficient alveolarisation * chILD related to chronic aspiration * chILD related to immunodeficiency * chILD related to abnormalities in lung vessel structure * chILD related to organ transplantation/organ rejection/GvHD * chILD related to recurrent infections * Acute severe infectious exacerbations * Known hypersensitivity to HCQ, or other ingredients of the tablets (lactose-monohydrate, povidone, maize starch, magnesium stearate, hypromellose, macrogol or titanium dioxide (E 171), silicon dioxide or mannitol), to sucrose-octaacetate or sodium saccharine. * Proven retinopathy or maculopathy * Glucose-6-phosphate-dehydrogenase deficiency resulting in favism or hemolytic anemia * Myasthenia gravis * Hematopoetic disorders * Pregnancy and lactation (Women with childbearing potential have to practice a medically accepted contraception during trial and till three months after the end of the treatment with HCQ, and a negative pregnancy test (serum or urine) should be existent on Visit 1, if girls of childbearing age and only if sexual relations are known or probable. It is at the discretion and responsibility of the attending physician to decide, whether a pregnancy test is necessary or not. Reliable contraception are systematic contraceptives (oral, implant, injection). Women that are sterile by surgery can participate in the trial. At the discretion of the investigator, sexual abstinence is also accepted as contraceptive method. Girls after menarche have to receive a counselling about birth control methods in presence of at least one parent, which has to be documented in the patient notes. * Participation in other clinical trials during the present clinical trial or not beyond the time of 4 half-lives of the medication used, at least one week. * Hereditary galactose intolerance, lactase deficiency or glucose-galactose- malabsorption * Renal insufficiency at screening, defined as glomerular filtration rate (GFR) * \< 40 mL/min/1.73 m2 in patients age 3 to 8 weeks * \< 60 mL/min/1.73 m2 in patients ≥ 8 weeks of age (KDIGO guideline 2012, K/DOQI guideline 2002) * Liver disease, gastrointestinal disorder, haematological disorder, epilepsy or other neurological disorder, psoriasis, porphyria at the discretion of the treating physician * Simultaneous prescription of other potentially nephrotoxic or hepatotoxic medication at the discretion of the treating physician