Rare, Simultaneous NMOSD Diagnosis Seen in Identical Twins

Somi Igbene, PhD avatar

by Somi Igbene, PhD |

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A case report has detailed the clinical journeys of two identical twin sisters’ simultaneous diagnosis with neuromyelitis optica spectrum disorder (NMOSD), a rare occurrence.

NMOSD was last reported in identical twin sisters in 1938, but those girls’ symptoms started two years apart,  unlike the present case.

The case report, “Simultaneous new onset of neuromyelitis optica spectrum disorder in identical twins,” was published in BMJ Neurology Open.

NMOSD is an autoimmune condition that causes inflammation in the spinal cord and optic nerves, the nerves connecting the eyes to the brain. It usually occurs on its own, but patients may also have an accompanying autoimmune disease, such as hypothyroidism (a defective production of thyroid hormones), myasthenia gravis, and anemia.

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An NMOSD diagnosis is given if an MRI scan detects inflammation in the optic nerves, spinal cord, or particular brain regions, along with a positive test for autoantibodies that target the water channel aquaporin-4 (AQP4-IgG).

In the current case study, the sisters were 20-year-old African Americans with a family history of Leiden factor V mutation, which causes a blood clotting disorder, but no record of demyelinating diseases, including NMOSD.

Sister A developed normally but had hypothyroidism from age 9, irritable bowel syndrome, vitamin D deficiency, and the Leiden factor V mutation. In the two weeks before her visit, she developed slight pain in her right eye with uncontrolled eye movements, which progressed to blurred vision nine days later. Her ophthalmologist suspected optic neuritis, which was confirmed by a subsequent MRI scan.

Tests for AQP4-IgG in her cerebrospinal fluid (CSF), the liquid that surrounds the brain and spinal cord, and in her blood were positive. She had no other infections or abnormal cells and her protein and glucose levels were normal.

Two weeks later, another MRI scan revealed lesions within her spinal cord’s thoracic region. She was treated with intravenous methylprednisolone, a steroid medication that lowers inflammation, for five days, and her vision returned to normal after 18 days.

Sister B also developed normally and had hypothyroidism and the Leiden factor V mutation. Six weeks before her neurological exam, she began having visual hallucinations before falling asleep, which her physician attributed to a urinary tract infection. Antibiotics resolved her visual symptoms for a couple of weeks, but she began having double vision a few days before her examination.

Blood tests confirmed her hypothyroidism and revealed a vitamin B6 deficiency. MRI scans detected lesions in the cervical region of the spinal cord and in a part of the midbrain that regulates pain and is involved in responses to threats. The patient also had rotatory, involuntary eye movements and impaired horizontal eye movements.

Similar to her sister, tests for AQP4-IgG in the CSF and in blood samples came back positive. Tests for Lyme disease, bacterial, and viral infections were negative.

She was treated with intravenous methylprednisolone and tapered off with prednisone. She fully recovered after 12 days of treatment.

“This case is unique in that these identical twins presented essentially simultaneously with different clinical symptoms and different radiological findings, not matched in the literature since the original twin article in 1938 (they were two years apart),” the researchers wrote.

“Both had the spinal cord involvement, had hypothyroidism, Leiden factor V homozygous and had no previous symptoms,” they continued, adding that “both sisters had an excellent response and recovery after intravenous methylprednisolone treatment.”