Neurofibromatosis type 1: when the skin hides a spinal cord emergency

A young man of 25 years old. Spots on the skin known since childhood. And then, gradually, a paralysis sets in. The medical reflex is immediate: look for a lesion in the brain. The brain MRI is performed, it comes back normal. It’s imaging of the spinal cord that finally gives the answer and it changes everything.

This clinical case, presented by Sako Aboubacar Sidiki and Dr Aïssatou Diallo during the 6th Days of the Guinean Society of Dermatology in Conakry, poses a fundamental question that every clinician should keep in mind: paralysis on one side of the body is not necessarily of cerebral origin.

A genetic disease much more common than we think

Neurofibromatosis type 1, or NF1, is often presented as a rare disease. The numbers tell a different story. A meta-analysis published in 2023 in the journal Orphanet Journal of Rare Diseases, based on twenty international studies, establishes the prevalence of NF1 at approximately 1 in 3,164 people worldwide (https://pmc.ncbi.nlm.nih.gov/articles/PMC10500831/). Other sources place its incidence at one in 3,500 births, making it one of the most widespread autosomal dominant genetic diseases in the world (ScienceDirect, 2022).

In Guinea, as in several other sub-Saharan African countries, it is most likely underdiagnosed, due to lack of sufficient awareness and suitable technical platforms.

The disease is caused by a mutation in the NF1 gene, located on chromosome 17. This gene normally produces a protein called neurofibromin, which functions as a natural brake on cell multiplication. When this brake lets go, benign tumors, neurofibromas, can form anywhere in the body: under the skin, along the nerves, inside the spine. Around half of affected people are victims of a mutation that occurs spontaneously, without any known family history, which considerably complicates early detection.

The first visible signs are cutaneous: characteristic café-au-lait colored spots, nodules under the skin, particular pigmentation of the armpits. It is usually these signs that lead to the initial diagnosis, a diagnosis that too often stops there.

When the spinal cord takes the clinician by surprise

This is precisely what happened to this 25-year-old patient, already being treated for NF1. Two months before his hospitalization, he had undergone the removal of a neurofibroma in the lumbar region, an intervention with no apparent link to what would follow. Then the neck pain appeared. Then progressive weakness on the left side of the body, affecting both the arm and the leg. The neurological examination showed the classic signs of damage to the motor pathways: tense muscles, exaggerated reflexes, motor deficit.

The brain MRI, carried out as first intention, showed nothing abnormal. It is the MRI of the cervical spine which reveals the cause: a neurofibroma compressing the spinal cord between the C2 and C4 vertebrae, pushing it backwards.

This type of presentation, spinal cord compression revealing NF1, remains rare but documented in the international literature, including in patients with no known family history (PMC, 2023) https://pmc.ncbi.nlm.nih.gov/articles/PMC10336349/. The lesson that the authors draw from this is clinically valuable: in the context of NF1, any progressive paralysis must suggest spinal cord compression, not just brain damage.

Warning signs to never ignore

Spinal cord damage represents less than 5% of symptomatic forms of NF1, but it is among the most serious. Upper cervical lesions particularly expose you to a risk of respiratory dysfunction, due to their proximity to the brainstem (PMC, 2022) https://pmc.ncbi.nlm.nih.gov/articles/PMC9398895/. The spinal cord only has a very limited space before being compressed, and once the neurological after-effects have set in, they can be irreversible.

Sako Aboubacar Sidiki and Dr Aïssatou Diallo identify several warning signals which should lead immediately to imaging in any patient monitored for NF1 “progressive weakness or loss of sensation in a limb, persistent pain in the back or neck, difficulty walking, or problems with sphincter control. Faced with these symptoms, spinal cord MRI is not an option to consider, it is a diagnostic emergency.”

A disease that is never the same

This case also illustrates one of the most complex challenges of NF1: its extraordinary clinical variability. Two patients carrying the same mutation can present radically different clinical pictures. Complications and prognosis are highly variable, and patients with NF1 have a reduced life expectancy of ten to fifteen years compared to the general population (Orphanet / NCBI, 2020) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6998847/, mainly due to the increased risk of malignancies.

For African clinicians, this case is a strong reminder, “the management of NF1 cannot stop at dermatological follow-up. It requires permanent neurological vigilance and collaboration between dermatologists, neurologists and neurosurgeons, an interdisciplinarity that is still difficult to organize in health systems with limited resources. explained.

A systemic question beyond the individual case

The case presented by Sako Aboubacar Sidiki and Dr Aïssatou Diallo goes beyond simple medical curiosity. It asks a question that African health systems cannot continue to ignore: how many spinal cord compressions linked to NF1 are confused with strokes, due to lack of access to spinal MRI? How many patients permanently lose the use of their limbs because the diagnosis is made too late?

The response involves training front-line clinicians, raising awareness of NF1 polymorphism and strengthening imaging platforms. Huge projects, which the Guinean Society of Dermatology Days contribute, case by case, to making visible.