Ochronotic rheumatism in Algeria: clinical, radiological, biological and molecular studies--a case study of 14 patients in 11 families

OBJECTIVES: To confirm alkaptonuria and ochronotic arthropathy diagnosis by mutation screening of the homogentisate 1,2-dioxygenase (HGD) gene. Try to establish a genotype-phenotype correlation in the five subjects with a molecular study on HGD gene. METHODS: We report 14 alkaptonuria cases (10 men and four women) in 11 Algerian families. Consanguineous matings were evidenced in only three families (F = 1/16). Molecular analysis was performed by sequencing genomic DNA in order to identify the mutations of the HGD gene. RESULTS: Alkaptonuria was always confirmed by urinary homogentisic acid determination. Four different mutations of the HGD gene were found: an homozygous missense mutation, Serine189Isoleucine in two sisters with a mild phenotype; an homozygous splice site mutation (IVS1-1G > A) in a man with a severe phenotype (death at 61 years old from renal failure); a silent mutation, Alanine470Alanine at the heterozygous state in a man with a mild phenotype; a 'G' deletion at the position c.819 which causes a frameshift after Gly217(Gly217fs) that runs into a stop codon at c. 850. This mutation is novel and was found in heterozygosis in a woman with a mild phenotype. CONCLUSIONS: The two homozygous mutations were associated, respectively, with a severe and a mild phenotype but no genotype-phenotype correlation could be found.