Faheema Hasan: Chronic Methemoglobinemia Causing Longstanding Tissue Hypoxia and Secondary Erythrocytosis
Faheema Hasan, Associate Professor at United Medicity, shared a post on LinkedIn about a recent article by Naseema Gangat et al, published in American Journal of Hematology, adding:
“Hematology is humbling.
Nothing replaces diligent clinical examination
I recently saw a middle aged male patient referred for evaluation of erythrocytosis.
- Hb 21 g/dL
- TLC 8,900/µL
- Platelets 5 lakh/µL
Peripheral smear otherwise unremarkable.
Marked plethora, no organomegaly.
No smoking, no prior treatment.
The textbook work-up for polycythemia followed:
- EPO greater than 100 mIU/mL (elevated)
- JAK2 — negative
Then further investigations pursued
- SPEP — normal
- ECHO — normal
- Low-dose CT (head/neck, thorax, abdomen) — no pathology
The diagnosis remained elusive.
Because his haematocrit was over 60%, I wanted to re-examine him personally. That second look changed everything.
The patient had deeply pigmented skin. His lips appeared unusually dark, and when I asked further, he said they had looked that way ‘for as long as he could remember’.
As a farmer, his nails were discoloured from years of working with soil — masking another clue.
Cyanosis — that classic grey-blue hue we are trained to recognise — was hidden in plain sight.
I sent an arterial blood gas with methemoglobin estimation.
22% Methemoglobin
Normal: < 1–2%
The final diagnosis:
Chronic methemoglobinemia causing longstanding tissue hypoxia and secondary erythrocytosis.
How and how important and indispensible is clinical examination..
And this paper on Jak negative erythrocytosis is exemplary!!
Work up for cause of possible congenital methemohlobinemia is underway.”
Title: JAK2 Unmutated Erythrocytosis: 2026 Update on Diagnosis and Management
Authors: Naseema Gangat, Natasha Szuber, Ayalew Teffer
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