Nadir bir Hipoksemi Sebebi; Herediter Methemoglobinemi

Abstract

Herediter Methemoglobinemi hpokseminin nadir sebeplerinden biridir. CYB5R3 geninde oluşan mutasyonlar otozomal resesif herediter methemoglobinemiye neden olur. Çoğunlukla nefes darlığı, morarma, halsizlik gibi semptomlar görülebilir. Bazen erişkin yaşa kadar semptom vermeyebilir. Onsekiz yaşında ellerinde ve dudaklarında zaman zaman tekrarlayan morluk, nefes darlığı, çarpıntısı olan olgumuzun, oksijen satürasyonu (Sa02) %85 saptandı. Methemoglobin (Methb) düzeyi %20 (N;0-1.5) idi. Dispne ve siyanozu açıklayacak kardiyak ve pulmoner neden saptanmayan olguda satürasyonu düşüklüğü ve methb yüksekliği nedeniyle methemoglobinemi düşünülerek, yüksek doz ıntravenöz askorbik asit verildi. Satürasyonu yükselen ve methb düzeyi tedricen düşen hastanın takiplerinde genetik testler sonucunda CYB5R3 geni sekans analizi ile homozigot missense c.136C>T (p.R46W) mutasyonu saptandı. Hasta otozomal resesif herediter methemoglobinemi tip 1 olarak kabul edildi. Pulmoner ve kardiyovasküler nedenlerle açıklanamayan nefes darlığı, hipoksi, siyanoz birlikteliğinde nadir görülen herediter methemoglobineminin akla gelmesi gerektiğini vurgulamak için bu vakamızı sunuyoruz.

Keywords

• Herediter Methemoglobinemi
• CYB5R3 Gen Mutasyonu
• Hipoksemi
• Dispne
• Siyanoz

A Rare Cause of Hypoxemia: Hereditary Methemoglobinemia

Abstract

Hereditary methemoglobinemia is one of the rare causes of hypoxemia. Mutations in the CYB5R3 gene cause autosomal recessive hereditary methemoglobinemia. Mostly, symptoms such as shortness of breath, bruise and and fatique occur. It may not display any symptoms until adult ages. Our case was at the age of 18 and had sometimes recurring bruise in hands and lips, shortness of breath, palpitations and oxygen saturation (SaO2) was 85%. Methemoglobin (Methb) level was %20 (N;0-1.5) No cardiac or pulmonary cause could be detected, which could account for dyspnea and cyanosis, and due to low saturation and high Methb. levels, metheglobinemia was considered and high dose IV ascorbic acid was administered. In follow up period, saturation increased and Methb. level gradually decreased and with genetic tests, homozygous missense c.136C> T (p.R46W) mutation was detected with CYB5R3 gene sequence analysis. Patient was diagnosed with autosomal recessive hereditary methemoglobinemia type 1. This case is presented ın order to emphasize that hereditary methemoglobinemia should be kept in mind when shortness of breath, hypoxia and cyanosis, occur together and can not be attributed to pulmonary and cardiovascular causes.

Keywords

• Hereditary methemoglobinemia
• CYB5R3 Gene Mutation
• Hypoxemia
• Dyspnea

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