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Ultra‐orphan lysosomal storage diseases: A cross‐sectional quantitative analysis of the natural history of alpha‐mannosidosis
Author(s) -
Zielonka Matthias,
Garbade Sven F.,
Kölker Stefan,
Hoffmann Georg F.,
Ries Markus
Publication year - 2019
Publication title -
journal of inherited metabolic disease
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.462
H-Index - 102
eISSN - 1573-2665
pISSN - 0141-8955
DOI - 10.1002/jimd.12138
Subject(s) - enzyme replacement therapy , natural history , medicine , cohort , lysosomal storage disease , survival analysis , pediatrics , age of onset , young adult , retrospective cohort study , disease
Alpha‐mannosidosis (OMIM 248500) is a rare lysosomal storage disorder caused by a deficiency of the enzyme alpha‐mannosidase. Recently, enzyme replacement therapy was approved in the European Union for the treatment of alpha‐mannosidosis, but evaluation regarding long‐term efficacy and safety is hard to assess due to missing quantitative natural history data, in particular survival. We performed a quantitative analysis of published cases (N = 111) with alpha‐mannosidosis. Main outcome measures were age of disease onset, diagnostic delay and survival (overall and by subgroup exploration). Residual alpha‐mannosidase activity and age of onset were explored as potential predictors of survival. STROBE criteria were respected. Median age of onset was 12 months. Median diagnostic delay was 6 years. At the age of 41 years 72.3% of patients were alive (N = 111). Residual alpha‐mannosidase activity (N = 34) predicted survival: Patients with a residual alpha‐mannosidase activity below or equal to 4.5% of normal in fibroblasts had a median survival of 3.5 years, whereas patients with alpha‐mannosidase activity above this threshold all survived during the observation period reported. Patients with age of onset above 7 years survived significantly longer than patients with age of onset below or equal to 7 years. Patient distribution was panethnic with hotspots in the United States and Germany. We defined age of onset, diagnostic delay, and survival characteristics in a global cohort of 111 patients with alpha‐mannosidosis by retrospective quantitative natural history modeling. These data expand the quantitative understanding of the clinical phenotype.