Post-mortem Diagnosis of Heme Oxygenase-1 Deficiency by Whole Exome Sequencing in an Iranian Child

Heme oxygenase-1 (HO-1) is an inducible enzyme involved in the catalysis of heme conversion into biliverdin. We describe a patient with a novel stop-gain mutation in the HMOX1 coding sequence resulting in HO-1 deficiency. A 17-month-old female with fever, tachypnea, and signs of respiratory distress was referred to our center. Four admissions ensued during the eight months follow up. At the first admission, she had massive pericardial effusion without any laboratory findings for tuberculosis, viral infectionsor malignancies.An abdominal ultrasound examination confirmed hepatomegaly.Laboratory findings showed leukocytosis, thrombocytosis, hemolytic anemia, elevated inflammatory markers, increased levels of the hepatic transferase, triglycerides and ferritin as well as decreased level of fibrinogen. Other laboratory investigations were negative blood cultures, normal bone marrow aspiration, and normal serology viral infections. Immunodeficiency and auto-inflammatory syndromes were ruled out. Hepatic biopsy showed iron deposits. The patient was initiated on corticosteroids; however, her clinical condition was progressively deteriorated, and she died of recurrent fever, bleeding, heart failure, and ascites. Post-mortem whole exome sequencing revealed a homozygous mutation (exon3: c.A610T, p.K204X) on the HMOX1 gene. The parents were found to be heterozygous for that mutation. The laboratory findings and clinical features of our patient were somehow similar to that of HO-1 deficient cases reported previously, as well as Hmox1 knocked out mice. We speculate that the clinical manifestations of HO-1 deficient patients can be partially dependent on the type of mutation they inherit.