Cogan's syndrome

Cogan's syndrome is a rare inflammatory disease of unknown cause, classified among the systemic vasculitides, which affects the cornea and the inner ear by preference ⁴.

It mainly affects young adults, with a sex ratio close to one, and it runs a relapsing course of ocular and ear, nose and throat flares that may occur together or in isolation ⁴.

Its prognosis does not rest on the eye, whose involvement usually resolves with full recovery of visual acuity, but on the inner ear, where the damage can be severe and irreversible ⁴.

Arsène Mekinian's work on this disease covers its description at national level, the retrospective assessment of its treatments, and the writing of the French national diagnosis and care protocol, which he coordinated.

Involvement of the eye and involvement of the inner ear

The characteristic ocular lesion is non-syphilitic interstitial keratitis, that is to say deep inflammation of the cornea unrelated to syphilis. It is usually bilateral from the outset, or becomes so during the course, and presents as a red and painful eye, sometimes with reduced visual acuity ⁴.

Inner ear involvement is likewise bilateral from the outset in most cases. It combines the abrupt onset of continuous rotatory vertigo, tinnitus and rapidly progressive sensorineural deafness, a picture close to that of Ménière's disease ⁴.

Either of these two manifestations may be the presenting one and remain isolated at first, which is why a patient is often seen first by an ophthalmologist or by an ear, nose and throat specialist before the disease is referred to a general cause ⁴.

Between about thirty and seventy per cent of patients have systemic manifestations, in particular deterioration of general condition and fever. A biological inflammatory syndrome is present in seventy-five per cent of cases ⁴. Association with other autoimmune diseases is possible, in particular with other vasculitides such as polyarteritis nodosa or Takayasu arteritis ⁴.

Typical form and atypical form

The distinction between typical and atypical form organises the description of the disease, and it rests on a two-year interval between the two organ manifestations.

The form is called typical when non-syphilitic interstitial keratitis is associated with cochleovestibular involvement resembling Ménière's disease, with a maximum interval of two years between the two ^{2, 5}.

It is called atypical in the absence of interstitial keratitis and in the presence of other inflammatory ocular manifestations, or when the cochleovestibular involvement does not resemble that of Ménière's disease, or again when the interval between the two manifestations exceeds two years ^{2, 5}.

This distinction is descriptive. It does not constitute a validated diagnostic criterion, and the 2025 review recalls that there is neither a diagnostic criterion nor a specific biomarker allowing the disease to be affirmed ⁵.

A diagnosis of exclusion

Cogan's syndrome is presumed to be autoimmune in mechanism, but no specific autoantibody has been identified ⁴.

The diagnosis is therefore one of exclusion, made after a methodical search designed to rule out other causes ⁵. Markers of inflammation are often present, but no laboratory test is specific to the disease ².

The Orphanet entry devoted to the disease, which is not his, describes the same approach: the diagnosis is mainly clinical, aims to rule out infection, syphilis and Lyme disease first of all, and no test can confirm it, even though laboratory tests, audiometry and imaging help to support it. It places in the differential diagnosis syphilis, Ménière's disease, Lyme disease, sarcoidosis, tuberculosis, polyarteritis nodosa, granulomatosis with polyangiitis and Takayasu arteritis [source C].

The French national diagnosis and care protocol

On 22 April 2024 the Haute Autorité de santé published online a national diagnosis and care protocol devoted to Cogan's syndrome, in the form of a chronic disease guide accompanied by three documents: the protocol itself, its background paper and a summary for the general practitioner [source B].

This text was drawn up under the aegis of the reference centre for autoinflammatory diseases and inflammatory amyloidosis (CeRéMAIA) and of the rare autoimmune and autoinflammatory disease network (FAI²R) [sources A and B]. The page that FAI²R devotes to this text writes that "it was drafted under the coordination of Prof. Arsène MEKINIAN" [source A].

The Haute Autorité de santé states on the same page that the protocol was drawn up using a methodology it provides, but that it has not been validated by the agency and that the agency did not take part in drawing it up [source B]. That sentence is reproduced here because it describes exactly the status of the document: a national diagnosis and care protocol organises the management of a rare disease, it is not the conclusion of an assessment conducted by the Haute Autorité de santé.

The published version of the protocol appeared in English in La Revue de médecine interne in February 2025, under the title French protocol for diagnosis and management of Cogan's syndrome. The MEDLINE record classifies it as Practice Guideline and Review. It carries twenty-six named authors; Arsène Mekinian is the twenty-sixth and last, and he is the only one whose record carries a corresponding email address. The first twenty-five are listed in alphabetical order, which is the convention for consensus texts and not an order of contribution. Six of the twenty-six signatories work in the department of internal medicine of Saint-Antoine Hospital according to the addresses on the record, and the others come from internal medicine, rheumatology, ophthalmology, ear, nose and throat medicine, paediatrics, dermatology and a patients' association ⁴.

The Orphanet entry for Cogan's syndrome contains, under its heading "clinical practice guidelines", only two items: the French national protocol of 2024 and its English publication of 2025 [source C]. That is an observation about the content of that entry on the date it was read; it is not a demonstration that no international recommendation exists.

What the French national study shows

The protocol draws on a French national study published in 2017 in Autoimmunity Reviews, of which Arsène Mekinian is the twenty-fourth and last of twenty-four named authors, and the only one carrying a corresponding email address ¹.

The study brings together forty French patients and twenty-two cases from the literature, that is sixty-two patients, of whom thirty-one were women, with a median age of thirty-seven years and extremes of two and seventy-six years ¹.

At diagnosis, sixty-one of the sixty-two patients, that is ninety-eight per cent, had vestibuloauditory symptoms, with bilateral deafness in forty-one per cent and deafness in thirty-one per cent. Ocular signs were present in fifty-seven patients, that is ninety-two per cent, including interstitial keratitis in thirty-one of them, that is fifty-one per cent ¹.

First-line treatment consisted of corticosteroids alone in forty-three patients, that is seventy per cent, and of corticosteroids combined with an immunosuppressant in eighteen patients, that is thirty per cent. The vestibuloauditory response did not differ between the two strategies: thirteen patients out of forty-three, that is thirty per cent, against four out of eighteen, that is twenty-two per cent, with a p value of 0.8. Ocular responses, thirty-two out of thirty-nine against fifteen out of nineteen, and systemic responses, twenty-three out of twenty-eight against ten out of fourteen, did not differ either ¹.

In all, sixty-one patients received one hundred and twenty-six treatment lines: fifty-one lines of corticosteroids alone, sixty-five lines of corticosteroids combined with a conventional disease-modifying drug and ten lines of infliximab. The vestibuloauditory response was more frequent under infliximab than under a conventional disease-modifying drug or under corticosteroids alone, eighty per cent against thirty-nine and thirty-five per cent, whereas ocular, systemic and biological responses were comparable. Infliximab was the only significant predictive factor of vestibuloauditory improvement, with an odds ratio of 20.7, a ninety-five per cent confidence interval of 1.65 to 260 and a p value of 0.019 ¹.

The authors themselves conclude that infliximab might allow a vestibuloauditory response in forms refractory to corticosteroids and to disease-modifying drugs, but that prospective studies remain necessary ¹. The section "What remains to be demonstrated" returns to the exact scope of that result.

The review articles

Three review articles complete this body of work and cover fifteen years of description of the disease.

A review in French, published in La Revue de médecine interne in April 2021 after online publication on 7 August 2020, of which he is first of four named authors and the only one carrying a corresponding email address. It sets out the distinction between typical and atypical form and the two-year threshold between the two organ manifestations, notes the possibility of large-vessel involvement affecting mainly the thoracic aorta, and concludes that the place of immunosuppressants and biologics combined with corticosteroids remains to be determined ².

A review in French published in Revue du Rhumatisme in October 2023, of which he is second and last of two authors. That journal is not indexed under this title in PubMed: the author position was taken from the Crossref database, and not from a MEDLINE record ³.

An English-language review published in the European Journal of Internal Medicine in 2025, of which he is fourth and last of four named authors. It recalls that there is neither a diagnostic criterion nor a specific biomarker, that the diagnosis remains one of exclusion, that prognosis rests on the risk of deafness and blindness as well as on the complications of the vasculitis, and that the only therapeutic data available come from isolated cases and from series ⁵.

Not to be confused with two homonyms

Three entities carry the name Cogan and do not designate the same disease. The confusion is frequent in online searches and is worth clearing up.

Cogan's syndrome as described on this page is registered under code ORPHA 1467, with codes ICD-10 H16.3 and ICD-11 4A44.Y [source C].

Cogan-Reese syndrome is a form of iridocorneal endothelial syndrome, characterised by iris atrophy, pigmented pedunculated iris nodules and corneal abnormalities, of which secondary glaucoma is a frequent complication. It is registered under code ORPHA 98980, ICD-10 code H21.2. It is a disease of the eye unrelated to the inner ear [source D].

Cogan-type oculomotor apraxia is a neurological syndrome of childhood, characterised by an abnormality in the initiation of voluntary horizontal eye saccades, whose manifestations generally lessen with age. It is registered under code ORPHA 1125, ICD-10 code H51.8 [source E].

Care across three specialties

Care is multidisciplinary by construction, because the disease declares itself in two organs followed by two different specialties.

It brings together the ophthalmologist for the corneal involvement, the ear, nose and throat specialist for the cochleovestibular involvement and the internist for the systemic and vascular involvement and for the conduct of long-term treatment. The signatories of the national protocol indeed come from these three specialties, to which rheumatology and paediatrics are added ⁴.

Patients are followed in the department of internal medicine of Saint-Antoine Hospital, AP-HP, Sorbonne Université. The national protocol was drawn up under the aegis of CeRéMAIA and of the FAI²R network [sources A and B]. Requests for advice between practitioners go through the department's secretariat.

What remains to be demonstrated

The state of knowledge is explicitly incomplete, and it is his own texts that say so. There is neither a validated diagnostic criterion nor a specific biomarker, no autoantibody is specific to the disease, and the diagnosis remains one of exclusion ^{4, 5}.

No prospective randomised study has been conducted to date. The national protocol writes it itself: therapeutic management lacks consensus for want of a study of this kind, and its proposals rest on retrospective series and on published cases ⁴. A national diagnosis and care protocol is a document organising care, not the conclusion of a trial.

The most quoted result of this body of work needs to be read with its limits. The superiority of infliximab for the vestibuloauditory response comes from a retrospective study that pools forty French patients and twenty-two cases from the literature, with only ten lines of infliximab. Its confidence interval, from 1.65 to 260, is very wide, which reflects an imprecise estimate. The patients treated with infliximab received it after other treatments had failed and were not randomised: the choice of treatment depended on the physician and on the patient's condition, which exposes the analysis to indication bias. The authors themselves conclude that prospective studies are necessary. This result therefore does not say what should be done for a given patient, and it promises no recovery of hearing ¹.

A negative result from the same work deserves to be written down. Adding an immunosuppressant to corticosteroids in first line did no better than corticosteroids alone on the vestibuloauditory response, thirty per cent against twenty-two per cent, with a p value of 0.8, nor on the ocular response, nor on the systemic response ¹. The comparison is made on small numbers and its absence of difference does not demonstrate equivalence: it does not allow a conclusion either way.

None of the drugs mentioned holds a marketing authorisation in Cogan's syndrome. Their use here follows a case-by-case decision, taken within the framework of the national protocol and after informing the patient of that level of uncertainty.

The true frequency of the disease is not known. The Orphanet entry, which is not his, gives a prevalence of one to nine cases per million inhabitants while stating that the true prevalence is unknown and that about three hundred cases have been reported to date, with a median age at onset between twenty and thirty years. That entry carries August 2019 as the date its summary was last updated, five years before the national protocol to which it refers [source C].

Finally, a caveat on the scope of the page itself. Three of the five works cited here are review or consensus texts, not original work. The only original work in the body is the 2017 study. The description of the disease given on this page therefore comes for the most part from a literature of cases and series, and it will change if a prospective study is one day conducted.

References

Published work he has taken part in, on this subject.

• Cogan syndrome: Characteristics, outcome and treatment in a French nationwide retrospective study and literature review — Autoimmunity Reviews, 2017 24th of 24 named authors, last author and the only corresponding author
• Syndrome de Cogan — La Revue de médecine interne, 2021 1st of 4 named authors, corresponding author. Article in French, published online on 7 August 2020
• Syndrome de Cogan — Revue du Rhumatisme, 2023 2nd of 2 named authors, last author. Journal not indexed under this title in PubMed, no PMID; position taken from Crossref
• French protocol for diagnosis and management of Cogan's syndrome — La Revue de médecine interne, 2025 26th of 26 named authors, last author and the only corresponding author. MEDLINE type Practice Guideline and Review. Published version of the national protocol put online by the Haute Autorité de santé on 22 April 2024
• Cogan's syndrome. A comprehensive review — European Journal of Internal Medicine, 2025 4th of 4 named authors, last author

General information only. This page does not replace individual medical advice. Updated: 14 September 2026.