Hereditary methemoglobinemia caused by Hb M-Hyde Park (Hb M-Akita) (HBB:c.277C > T; p.His93Tyr).

Healthy human blood contains only a trace amount of methemoglobin (Hb M), less than 1%. In Hb M iron is present in the oxidized ferric state (Fe³⁺) not in the reduced ferrous form (Fe²⁺) and this reduces the ability of hemoglobin to bind oxygen. The described rare hemoglobin variant Hb M‑Hyde Park (also known as Hb M-Akita) results from the substitution of amino acid tyrosine by histidine at position 93 of the beta-globin chain of hemoglobin. The rare Hb variant Hb M‑Hyde Park (Hb M‑Akita) is mainly inherited autosomal dominant and causes methemoglobinemia. Due to the low frequency of inherited Hb M variants, the diagnosis is challenging. Here, we here report on a family with Hb M‑Hyde Park (Hb M‑Akita) whose members demonstrated Hb M > 10%, but were, asymptomatic except for chronic cyanosis. Due to human mobility and migration other hemogobin variants, such as beta-thalassemia minor have spread to Austria . A genetic combination of two different hemoglobin variants may result in severe anemia. Genetic counseling for patients with hemoglobin variants, including Hb M‑Hyde Park (Hb M‑Akita) and beta-thalassemia minor, is essential.