Severe aortic stenosis in systemic lupus erythematosus and mucopolysaccharidosis type II (Hunter's syndrome)

Causes of death in mucopolysaccharidoses

Mucopolysaccharidoses are inherited metabolic diseases caused by mutations in genes encoding enzymes required for degradation of glycosaminoglycans. A lack or severe impairment of activity of these enzymes cause accumulation of GAGs which is the primary biochemical defect. Depending on the kind of the deficient enzyme, there are 12 types and subtypes of MPS distinguished. Despite the common primary metabolic deficit (inefficient GAG degradation), the course and symptoms of various MPS types can be different, though majority of the diseases from the group are characterized by severe symptoms and significantly shortened live span. Here, we analysed the frequency of specific, direct causes of death of patients with different MPS types, the subject which was not investigated comprehensively to date. We examined a total of 1317 cases of death among MPS patients, including 393 cases of MPS I, 418 cases of MPS II, 232 cases of MPS III, 45 cases of MPS IV, 208 cases of MPS VI, and 22 cases of MPS VII. Our analyses indicated that the most frequent causes of death differ significantly between MPS types, with cardiovascular and respiratory failures being predominant in MPS I, MPS II, and MPS VI, neurological deficits in MPS III, respiratory issues in MPS IV, and hydrops fetalis in MPS VII. Results of such studies suggest what specific clinical problems should be considered with the highest priority in specific MPS types, apart from attempts to correct the primary causes of the diseases, to improve the quality of life of patients and to prolong their lives.

A deletion of IDUA exon 10 in a family of Golden Retriever dogs with an attenuated form of mucopolysaccharidosis type I

Background

Mucopolysaccharidosis type I (MPS‐I) is a lysosomal storage disorder caused by a deficiency of the enzyme α‐l‐iduronidase, leading to accumulation of undegraded dermatan and heparan sulfates in the cells and secondary multiorgan dysfunction. In humans, depending upon the nature of the underlying mutation(s) in the IDUA gene, the condition presents with a spectrum of clinical severity.

Objectives

To characterize the clinical and biochemical phenotypes, and the genotype of a family of Golden Retriever dogs.

Animals

Two affected siblings and 11 related dogs.

Methods

Family study. Urine metabolic screening and leucocyte lysosomal enzyme activity assays were performed for biochemical characterization. Whole genome sequencing was used to identify the causal mutation.

Results

The clinical signs shown by the proband resemble the human attenuated form of the disease, with a dysmorphic appearance, musculoskeletal, ocular and cardiac defects, and survival to adulthood. Urinary metabolic studies identified high levels of dermatan sulfate, heparan sulfate, and heparin. Lysosomal enzyme activities demonstrated deficiency in α‐l‐iduronidase activity in leucocytes. Genome sequencing revealed a novel homozygous deletion of 287 bp resulting in full deletion of exon 10 of the IDUA gene (NC_006585.3(NM_001313883.1):c.1400‐76_1521+89del). Treatment with pentosan polyphosphate improved the clinical signs until euthanasia at 4.5 years.

Conclusion and Clinical Importance

Analysis of the genotype/phenotype correlation in this dog family suggests that dogs with MPS‐I could have a less severe phenotype than humans, even in the presence of severe mutations. Treatment with pentosan polyphosphate should be considered in dogs with MPS‐I.

Unexpected coronary artery findings in mucopolysaccharidosis. Report of four cases and literature review

INTRODUCTION

The mucopolysaccharidosis syndromes are a group of lethal inherited disorders affecting multiple organ systems by the progressive deposition of glycosaminoglycan. Advances in treatment such as enzyme replacement and hematopoietic stem cell transplantation have significantly improved the outcome of these disorders. An in-depth understanding of the pathophysiology of heart disease in these disorders is essential since death from cardiac causes continues to be common. Epicardial coronary artery luminal narrowing from myointimal proliferation and glycosaminoglycan deposition is well described in severe mucopolysaccharidosis type I [Hurler syndrome, mucopolysaccharide IH] but poorly understood in other "non-Hurler" phenotypes of these disorders. Given the rarity of these conditions, autopsy specimens are uncommon.

METHODS

Tissue from epicardial coronary arteries from autopsies of four patients with non-Hurler mucopolysaccharidosis (attenuated type I, type IIIA, type IIIC, and type VI) who had died after hematopoietic cell transplantation (within 1 month in three cases; after 5 years in the fourth) was examined by light microscopy.

RESULTS

Unexpectedly, near-normal coronary arteries were observed in the patient with attenuated mucopolysaccharidosis type I, while the coronaries from patients with type IIIA, IIIC, and VI demonstrated classic histologic features of glycosaminoglycan deposition. The most severe findings were found in the MPS IIIC patient who had 5 years of full donor engraftment after transplantation.

CONCLUSIONS

Our current understanding of the cardiac manifestations of the mucopolysaccharidoses fails to explain why near-normal coronary arteries may be observed when abnormalities would be most likely to be expected and, conversely, why significant histopathology is present when it would be least expected. Identification of downstream effects of glycosaminoglycan deposition may identify other metabolites or metabolic pathways that are important in the clinicopathologic manifestations of these diseases.

SUMMARY

The mucopolysaccharidosis diseases are a group of inherited disorders affecting multiple organ systems by the progressive deposition of glycosaminoglycan. Severe coronary artery disease is well recognized in severe type I mucopolysaccharidosis (Hurler syndrome), but unexpected coronary artery disease occurs in other, "non-Hurler" mucopolysaccharidoses. Factors responsible for the development of coronary pathology in the mucopolysaccharidoses remain elusive.

Restricted joint range of motion in patients with MPS II: correlation with height, age and functional status

AIM

The aims of the study were to assess shoulder range of motion (ROM) in patients with mucopolysaccharidosis type II (MPS II) and to correlate joint mobility with patients' height, age and functional status.

METHODS

Passive ROM and Z-score of height were followed in 29 patients with MPS II (mean age 11.5 years, range 2-29 years) between the years 2005 and 2010. Passive ROM was measured by a goniometer, and height, by a stadiometer. Functional status was assessed by an age-appropriate health assessment questionnaire (HAQ).

RESULTS

(i) A strong correlation was observed between patients' age and Z-score of patients' height (R = 0.78, p < 0.001). (ii) A medium correlation was observed between Z-score of patients' height and passive shoulder flexion and abduction (R = 0.697, p < 0.001 and R = 0.63, p < 0.001, respectively). The progression of restriction was slower in attenuated patients. (iii) Restrictions in shoulder flexion and abduction were already observed before the second year of life. (iv) ROM limitations intensified and became more severe with age. (v) Activities of daily living depended on cognitive impairment of patients with MPS II.

CONCLUSION

Range of motion limitations in patients with MPS II correlate with patients' height, increase with patients' age and are more pronounced in a severe form of MPS II.

Left ventricular aneurysm, aortic valve disease and coronary narrowing in a patient with Hunter's syndrome

Hunter's syndrome (mucopolysaccharidosis type 2, MPS 2) is an inherited disorder of glycosaminoglycan degradation commonly associated with cardiac disease. We present the case of a young man with unusual cardiac manifestations of this syndrome. When mixed aortic valve disease was noted in childhood, other classical features of the milder form of Hunter's syndrome were present. There was no symptomatic or echocardiographic cardiovascular deterioration until age 27 when the patient presented in severe biventricular failure. Investigations demonstrated cardiomegaly and a large apical left ventricular aneurysm. The patient died suddenly soon after this diagnosis. Post mortem examination demonstrated a hypertrophied left ventricle with a 6-cm apical aneurysm. Coronary arterial walls were diffusely thickened but with only mild lumenal stenosis. Mitral and aortic valve disease was also present. There is one previous report of ventricular aneurysm in Hunter's syndrome. Pathophysiological contributions to aneurysm formation may include abnormal coronary flow, the presence of aortic stenosis and abnormal myocardium. This patient's sudden deterioration after a long period of clinical stability reinforces the need for careful follow-up of patients with cardiac manifestations of Hunter's disease.