Latar Belakang: Mukopolisakaridosis tipe IV A (MPS IV A, Morquio A syndrome) merupakan kelainan autosomal resesif yang disebabkan adanya mutasi pada gen N-acetylgalactosamine-sulfate sulfatase (GALNS atau galactosamine (N-acetyl)-6-sulfate sulfatase; MIM #612222). Diagnosis MPS IV A dapat dicurigai melalui pemeriksaan penapisan GAGs (glukosaminogikans) urin dan ditegakkan dengan pemeriksaan dan aktifitas enzim GALNS pada leukosit atau kultur fibroblast. Pemeriksaan molekuler diperlukan karena bervariasinya gejala klinis yang berhubungan dengan variasi mutasi pada gen GALNS. Namun, lokasi mutasi hot spot berbeda-beda antar daerah dan etnis, Heterogenitas ini dapat menjadi tantangan bagi interpretasi pemeriksaan molekular pasien dengan MPS IV sehingga perlu strategi diagnostik yang efektif biaya untuk menemukan mutasi penyebab kelainan MPS tipe IVA di Indonesia. Tujuan: Mengetahui profil fenotipe-genotipe pasien MPS tipe IV A di Indonesia. Metode: Penelitian ini adalah studi potong lintang yang dilakukan di Departemen Ilmu Kesehatan Anak RSCM-FKUI dan Human Genetic Cluster (HGRC) IMERI FKUI sejak tanggal 1 Januari-13 Desember 2019. 3. Data terkait fenotipe, yaitu anamnesis, pemeriksaan fisis (PF), dan pemeriksaan penunjang, diambil dari data rekam medis. Selanjutnya dilakukan pengambilan darah dalam tabung EDTA sebanyak 5 mL. Tahapan pemeriksaan molekular meliputi isolasi DNA, desain primer, PCR, sequencing, dan analisis varian. Kategori varian baru (novel) yang ditemukan akan dibuat berdasarkan panduan dari American College of Medical Genetics and Genomics (ACMG). Hasil: Total subjek penelitian adalah 7 pasien MPS tipe IV A di Indonesia yang berasal dari 5 kota berbeda. Subjek terdiri dari 2 pasien lelaki dan 5 pasien perempuan. Rentang usia saat pemeriksaan antara 2-17 tahun. Terdapat riwayat keluhan serupa pada kakak subjek 1 dan 6. Pada kelima pasien lain, awitan gejala mukopolisakaridosis disadari pada usia antara 2-3 tahun. Tidak ada riwayat konsanguinitas pada orangtua subjek penelitian. Seluruh subjek pada penelitian ini diklasifikasikan sebagai tipe berat. Manifestasi klinis yang ditemukan pada seluruh subjek penelitian adalah leher pendek, genu valgum, pectus carinatum, sendi yang longgar, serta gangguan pada cara berjalan. Tiga dari 7 subjek saat ini masih dapat berjalan tanpa alat bantu. Data aktivitas enzim dan glikosaminoglikans pada subjek tidak seragam karena tempat pemeriksaan berbeda dan menggunakan metode yang berbeda pula. Sebanyak 24 varian ditemukan pada 7 subjek. Sebagian besar varian ditemukan pada ekson 7 (29,2%), diikuti ekson 5, 10, dan 12 (masing-masing 16,7%), ekson 13 (sebesar 12,5%). Sisanya varian ditemukan pada ekson 1, 11 dan ekson 14 (masing-masing 4,2%). Sebagian besar varian yang ditemukan merupakan varian missense (54,2%), diikuti varian silent (45,8%), dan hanya 1 (4,2%) varian yang ditemukan berupa varian nonsense. Varian tersering yang ditemukan adalah varian c.708C>T yang ditemukan pada 5 subjek, diikuti oleh varian c.510T>C dan c.1354 T>C yang ditemukan pada 3 subjek. Berdasarkan hasil temuan varian terdapat 12 varian benign, 4 VUS, dan 8 varian patogenik. Terdapat 3 varian novel pada subjek penelitian, satu di antaranya adalah varian likely pathogenic, yaitu varian c.1348 G>A. Simpulan: Dari tujuh subjek dalam penelitian ini, ditemukan 8 varian patogenik, di antaranya terdapat 1 varian likely pathogenic baru. Sebanyak 9 dari 14 alel (64,3%) dapat ditemukan varian patogenik, sedangkan 5 varian patogenik lainnya belum ditemukan. Fenotipe paling berat dialami oleh subjek 4 yang memiliki tinggi badan T.

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Background: Mucopolysaccharidosis type IVA (MPS IVA, Morquio A syndrome) is an autosomal recessive disease which is caused by defect in the N-acetylgalactosamine-6-sulfate sulfatase gene (GALNS, galactosamine (N-acetyl)-6-sulfate sulfatase; MIM #612222). After urine glycosaminoglycan is performed as a screening tool, diagnosis is confitmed through measuring GALNS enzyme activity in leucocyte or fibroblast. Molecular testing is needed because clinical symptoms are variable. Mutation in GALNS gene are many and can be different in each ethnicity and country. This heterogeneity poses a challenge to the diagnosis of MPS IVA especially in Indonesia. Therefore, data on clinical spectrum and genetic mutation of MPS IVA in Indonesian population is needed. Aim: To determine the phenotype-genotype correlation of MPS IVA in Indonesia Method: Subjects were recruited from Department of Pediatrics, Cipto Mangunkusumo Hospital, while molecular testing was performed in the Human Genetic Cluster (HGRC) IMERI Faculty of Medicine Universitas Indonesia between Januari 1st until December 13th, 2019. Data on phenotype was evaluated from medical records. A 5 ml EDTA whole blood was then collected from the subjects. Molecular testing consists of DNA isolation, primer design, PCR, sequencing, and variant analysis. Novel variants are then classified according to guidelines from the American College of Medical Genetics and Genomics (ACMG). Results: A total of 7 subjects from 5 different cities was included in this study, consisting of 2 boys and 5 girls. Age at recruitments was between 2 to 17 years-old. Two subjects had history of MPS IVA in older sibling. Age of onset were between 2-3 years-old. No history of consanguinity in the subjects parents. All subjects were classified as severe type. Clinical manifestations found in all patients were short neck, genu valgum, pectus carinatum, loose joint, and difficulty walking. Three out of 7 subjects were still able to walk. Data on enzyme activity and glycosaminoglycans could not be compared because they were performed with different methods. Twenty four variants were found in 7 subjects. Mostly located on exon 7 (29.2%), followed by exon 5, 10, dan 12 (each 16.7%), exon 13 (12.5%), and the rest were found in exon 1, 11, and 14. Missense variants are the most commonly found (54.2%), followed by silent variants (45.8%), and 1 nonsense variant (4,2%). The most common variants found was c.708C>T in 5 subjects, followed by c.510T>C and c.1354 T>C, each on 3 subjects. These variants are classified as benign variants (50%), VUS (1.7%), and pathogenic variants (33.3%). Three novel variants were found in this study, including one likely pathogenic variants, c.1348 G>A. Conclusion: Eight pathogenic variant were found including one novel likely pathogenic variant. Nine out of 14 alleles (64.3%) were found. The most sever phenotype was found in subject 4 who had nonsense homozygous pathogenic variant c.751 C>T.