It started with his eyes. A 30-year-old man sought medical care after suddenly noticing that his pupils were different sizes. Doctors diagnosed an Adie tonic pupil, a pupil that responds sluggishly to light. Further examination found patches of skin that no longer sweated, other areas that sweated excessively to make up for them and missing tendon reflexes. Together, those findings pointed to Ross syndrome, a rare disorder of the nerves that run automatic body functions.
The unusual part came later. Over 15 years of follow-up, the side of his face that had been sweating too much turned pale and lost hair, in a pattern bounded by the midline of his face. Physicians affiliated with Universidad Anáhuac México reported the case online Aug. 3, 2026, in the Journal of Dermatology.
A Sudden Pupil Change Led to a Rare Nerve Diagnosis
Ross syndrome is defined by a triad: tonic pupils, reduced or absent deep tendon reflexes, and patches of skin that lose the ability to sweat. According to EyeWiki, the clinical encyclopedia of the American Academy of Ophthalmology, the condition was first reported in 1958, and only around 50 cases have been described. Counts vary by source, and other published reports have cited totals of fewer than 80 or fewer than 100.
The man's path to diagnosis was not unusual. In a Mayo Clinic review of 26 patients with confirmed Ross syndrome, 10 first noticed a tonic pupil, while 16 first noticed abnormal sweating, most often described as excessive sweating. The study, a chart review of patients who underwent a thermoregulatory sweat test between 1998 and 2020, found that fatigue, chronic cough, and frequent urination were also commonly reported. The loss of sweating progressed slowly, while heart rate and blood pressure control were preserved in most patients. Autoantibodies turned up in a minority, often with unclear significance, and only one patient had an associated autoimmune disease. The authors concluded that the pattern suggests a limited disease of the autonomic ganglia, clusters of nerve cells outside the brain and spinal cord.
That excess sweating is compensation. When nerves to some sweat glands stop working, other areas of skin work harder to release heat. The exact cause is unknown, according to DermNet, with dysfunction of sympathetic nerve fibers in the skin the leading proposed mechanism. The biology is still debated. One small study found deposits of alpha-synuclein, a protein tied to Parkinson's disease, in nerve endings of patients with Ross syndrome and proposed that the disorder may belong to the same disease family, an idea that has not been established.
Pale Skin and Hair Loss on the Side That Sweated Too Much
The new report adds a twist to that picture. The pallor and hair loss did not appear where sweating had stopped. They developed in the facial territory affected by compensatory hyperhidrosis, the area that had been sweating excessively.
The changes were one-sided and followed a pattern defined by the midline, the vertical center line of the face. The authors describe them as uncommon manifestations and say the case suggests Ross syndrome may involve "a broader spectrum of dermatological findings" than is widely recognized. They urge dermatologists to watch for skin changes linked to nerve disorders.
The published abstract does not establish why the skin turned pale or why hair was lost, and a single case cannot prove that Ross syndrome caused those changes rather than something coincidental. Further reports would be needed to show whether the pattern recurs in other patients.
Earlier Cases Hinted at Skin and Hair Changes
The pattern is uncommon, but it has some precedent. DermNet notes that pigment changes have been reported in Ross syndrome, typically darker skin where sweating is excessive and lighter skin where it has stopped. A report of two men, ages 35 and 58, published in 2019 described darker skin over the areas that sweated more, with mottled coloring that tracked the pattern of sweating.
An earlier case from India described darker skin in areas of excess sweating along with sparse hair on one side of a man's beard and mustache, features those authors said the medical literature did not explain.
In the new case, the overworking side of the face became paler rather than darker, and the hair loss followed the same territory. The contrast underscores how little is known about how this rare disorder affects the skin over the long term.
Overheating Is the Practical Concern for Patients
For people living with Ross syndrome, heat is the bigger day-to-day issue. EyeWiki notes that there is no cure and that the body's impaired temperature control can be dangerous. It recommends measures to prevent overheating for patients with symptoms, and it advises clinicians to check for involvement of other automatic body systems, including the digestive system and heart. Reported symptoms beyond the classic triad include sluggish digestion, sexual dysfunction and drops in blood pressure on standing.
DermNet says the syndrome can occur at any age, with presentation most common between 25 and 50, and that the first sign is usually a change in sweating. It describes the condition as benign and not life-threatening, although loss of sweating over large areas can lead to heat exhaustion and heat stroke, and general cooling measures such as loose clothing and avoiding hot environments are recommended.
Anyone who suddenly notices that their pupils are different sizes should seek prompt medical evaluation, since unequal pupils have many possible causes, some of them urgent. New patches of skin that no longer sweat, or unexplained one-sided sweating, are also worth raising with a clinician.
Key Questions Answered
What is Ross syndrome?
It is a rare disorder of the autonomic nervous system defined by tonic pupils, reduced or absent tendon reflexes, and patches of skin that cannot sweat, often with excessive sweating elsewhere.
What was unusual in this case?
Over 15 years, the man developed pale skin and hair loss on one side of his face, in the area that had been sweating excessively, with the changes bounded by the facial midline.
Did the syndrome cause the pale skin and hair loss?
The authors suggest the changes belong to the syndrome's range of skin findings, but a single case cannot prove cause, and the mechanism was not established.
How rare is Ross syndrome?
EyeWiki reports that only around 50 cases have been described since 1958, although some published counts are somewhat higher.
Is Ross syndrome dangerous?
It is generally described as benign, but impaired sweating can make overheating dangerous, so patients with symptoms are advised to take steps to stay cool.
What should someone do if their pupils suddenly look uneven?
Seek prompt medical evaluation. Unequal pupils have many causes, and some require urgent care.
