Samia Pichard, Nathalie Bednarek, Hélène Ogier de Baulny, Emmanuelle Le Trionnaire, Frédérique Sabourdy, Lionel Mourey, Vassili Valayannopoulos, Thierry Levade, Roselyne Garnotel, Catherine Caillaud, André Mégarbané, Yves Chaix, Roseline Froissart, Nathalie Guffon, Anne Dusser, Jean-Michel Pédespan, Marie-Ange Delrue, Alain Verloes, Institut Fédératif de Biologie (IFB) - Hôpital Purpan, Hôpital Purpan [Toulouse], CHU Toulouse [Toulouse]-CHU Toulouse [Toulouse], Centre de Recherches en Cancérologie de Toulouse (CRCT), Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Institut de pharmacologie et de biologie structurale (IPBS), Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées, Centre Hospitalier Universitaire de Reims (CHU Reims), CHU Necker - Enfants Malades [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), Imagerie cérébrale et handicaps neurologiques (ICHN), Institut des sciences du cerveau de Toulouse. (ISCT), Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-CHU Toulouse [Toulouse]-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratoire Maladies Rares: Génétique et Métabolisme (Bordeaux) (U1211 INSERM/MRGM), Université de Bordeaux (UB)-Groupe hospitalier Pellegrin-Institut National de la Santé et de la Recherche Médicale (INSERM), Hôpital Bicêtre, Hospices Civils de Lyon (HCL), Université Saint-Joseph de Beyrouth (USJ), Hôpital Robert Debré, Université de Bordeaux Ségalen [Bordeaux 2], Mourey, Lionel, Institut Fédératif de Biologie (IFB), Centre Hospitalier Universitaire de Toulouse (CHU Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre Hospitalier Universitaire de Toulouse (CHU Toulouse)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre Hospitalier Universitaire de Toulouse (CHU Toulouse)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)
Background Multiple sulfatase deficiency is a rare inherited metabolic disorder caused by mutations in the SUMF1 gene. The disease remains poorly known, often leading to a late diagnosis. This study aimed to provide improved knowledge of the disease, through complete clinical, biochemical, and molecular descriptions of a cohort of unrelated patients. The main objective was to identify prognostic markers, both phenotypic and genotypic, to accelerate the diagnosis and improve patient care. Methods The phenotypes of ten unrelated patients were fully documented at the clinical and biochemical levels. The long-term follow-up of each patient allowed correlations of the phenotypes to the disease outcomes. Each patient’s molecular defects were also identified. Site-directed mutagenesis was used to individually express the mutants and assess their stability. Characterisation of the protein mutants was completed by in silico analyses based on sequence comparisons and structural models. Results The most severe cases were characterised by the presence of non-neurological symptoms as well as the occurrence of psychomotor regression before 2 years of age. Nine novel SUMF1 mutations were identified. Clinically severe forms were often associated with SUMF1 mutations that strongly affected the protein stability and/or catalytic function as predicted from in silico and western blot analyses. Conclusions This detailed clinical description and follow-up of a cohort of patients, together with the molecular characterisation of their underlying defects, contribute to improved knowledge of multiple sulfatase deficiency. Predictors of a bad prognosis were the presence of several non-neurological symptoms and the onset of psychomotor regression before 2 years of age. No strict correlation existed between in vitro residual sulfatase activity and disease severity. Genotype–phenotype correlations related to previously reported mutants were strengthened. These and previous observations allow not only improved prediction of the disease outcome but also provision of appropriate care for patients, in the expectation of specific treatment development. Electronic supplementary material The online version of this article (doi:10.1186/s13023-015-0244-7) contains supplementary material, which is available to authorized users.