Mucopolysaccharidosis-I H (Hurler’s Disease): Biochemical defect: Homozygous or double heterozygous nonsense mutation of IDUA gene on Chromosome 4p encoding α-L-Iduronidase. Clinical features of MPS I H (Hurler’s Disease):Progressive disorder with multiple organ and tissue involvement that results in premature death, usually by 10 years of age. An infant with Hurler’s syndrome appears normal at birth, but inguinal hernias are often present. Diagnosis is usually made between 6 and 24 month of age. Hepatosplenomegaly, coarse facial features, corneal clouding, large tongue, prominent forehead, joint stiffness, short stature and skeletal dysplasia are seen. Acute cardiomyopathy has been found in some infants < 1 year of age. Most patients have recurrent upper respiratory tract and ear infections, noisy breathing and persistent copious nasal discharge. Valvular heart disease with incompetence, notably of the mitral and aortic valves, regularly develops, as dose coronary artery narrowing. Obstructive airway disease, notably during sleep, may necessitate trachotomy. Obstructive airway disease, respiratory infection and cardiac complications are the common causes of death. Key Concept: Hurler's disease is due to α-L- Iduronidase enzyme deficiency due to homozygous or double heterozygous nonsense mutation of IDUA gene on Chromosome 4p encoding α-L-Iduronidase. Reference- Harper’s illustrated biochemistry. 30th edition page no: 179