Biomarker-Guided Diagnosis of Riboflavin Transporter Deficiency Presenting as Seronegative Myasthenia Gravis: A Short Report from a Consanguineous Family.
Muhammad Wasim, Iram Javed, Guoda Ma
✦ AI-curated · Sources linked
Case in brief
A 3.5-year-old girl born to consanguineous parents developed bilateral ptosis, followed by dysphagia, dysphonia, facial diplegia, stridor, and respiratory compromise. Tongue atrophy with fasciculations and bulbar weakness, without limb weakness, were found. She had been diagnosed with seronegative myasthenia gravis but did not improve with corticosteroids, pyridostigmine, salbutamol, or intravenous immunoglobulin. Non-fluctuating symptoms, lower motor neuron signs, and a sibling history of hearing loss and bulbar palsy prompted testing, which identified a homozygous SLC52A3 variant of uncertain significance. High-dose riboflavin was followed by improved bulbar function, resolved stridor, and respiratory stabilization; ptosis and tongue fasciculations persisted.
What made this case unusual
Clinical improvement with riboflavin served as a functional clue to riboflavin transporter deficiency despite an SLC52A3 variant of uncertain significance, in a presentation initially mistaken for seronegative myasthenia gravis.
Diagnostic / clinical pearl
In a child with treatment-resistant, non-fluctuating ptosis and bulbar weakness, tongue atrophy or fasciculations and a family history of hearing loss or bulbar palsy should prompt consideration of riboflavin transporter deficiency.
Why it matters
The report illustrates how a riboflavin response may help interpret an uncertain genetic finding when the clinical picture suggests transporter deficiency.