Since the first description of hemoglobin Knossos (Hb b27 Ala®Ser) in a Greek family in 1982, as a silent b⁺ thalassemia variant, this Hb variant  has been observed in other families of Mediterranean origin (Turkey, Egypt, Algeria, Cyprus). It has been found in combination with other b thalassemia mutations: Cd 8,  IVS-I-1, IVS-I-6 and IVS-I-110, as well as in combination with Hb S and Hb Lepore. We have observed this Hb variant in association with codon 39 mutation in a Bulgarian patient in 1988. Here, we present the first Macedonian patient with thalassemia intermedia due to compound heterozygosity for Hb Knossos and IVS-I-6 mutation. The proband was a 8-months-old boy, when studied for the first time. He was reffered because of microcytic hypochromic anemia. The hematological analysis of the proband revealed Hb 7.0g/dl; PCV 0.23 l/l; RBC 4.3´10¹²/l; MCV 54 fl; MCH 16.3 pg.  No abnormal Hb was detected by starch gel electrophoresis. Routine DNA analysis (ASO hybridization for the most common mutations) revealed IVS-I-6 mutation in the proband and his father. Since the anemia persisted, the patient was reffered to us again at the age of five years. His hematological  and hemoglobin analysis showed: Hb 7.6g/dl; PCV 0.26 l/l; RBC 4.8´10¹²/l; MCV 54 fl; MCH 16.0 pg. Osmotic fragility was positive, n-butanol test for stability was negative; HbA₂ 3.9%; HbF 4.2%. An abnormal band, migrated between a and b chains, was detected by electrophoresis in 6M urea and Triton X-100 in the propositus and his mother. Direct DNA sequencing revealed that the propositus is compound heterozygous for Hb Knossos (Codon 27 GCC ®TCC) and IVS-I-6 mutation (T->C), while his mother is a carrier of Hb Knossos. 

Key words: Hb Knossos, IVS-I-6, b thalassemia intermedia.