A team from the Department of Ophthalmology and Visual Science at the Yokohama City University Graduate School of Medicine in Yokohama, Japan, recently published an online case report series that detailed three different clinical manifestations of tubulointerstitial nephritis and uveitis syndrome, or TINU.
Although rare, TINU occurs in both Asians and Caucasians. Since TINU was first reported in association with myeloid sarcoma in 1975, hundreds of cases unassociated with myeloid sarcoma have been reported.
Diagnostic criteria for TINU include uveitis and acute tubulointerstitial nephritis, itself a kidney disorder, confirmed histopathologically in the absence of systemic diseases like sarcoidosis, which are often associated with TIN, uveitis, or both. Patients with TINU usually have bilateral uveitis with an acute onset. Uveitis often becomes chronic or recurrent, and patients may have a slight fever, the most common systemic symptom of TINU.
TINU is most likely to affect girls who have not yet reached puberty. It affects females more than males (sex ratio, 2.5:1) and accounts for 1% to 2% of uveitis cases in children ≤15 years of age. However, it sometimes affects the middle-aged, in whom it tends to be chronic.
The first case in the series was that of a 15-year-old boy with left eye pain and iridocyclitis, reduced visual acuity, and flu-like symptoms. Hospital staff noted 1+ inflammatory cells in the anterior chamber, so they classified the disease as bilateral anterior uveitis. In addition, both eyes had fine keratic precipitates. These indicate that the uveitis is non-granulomatous, which differentiates early TINU from sarcoidosis-related uveitis, which is granulomatous.
Blood tests and urinalysis revealed elevated creatinine and markedly increased levels of β2-microglobulin (β2MG) and N-acetyl-β-D-glucosaminidase (NAG), a marker of renal dysfunction in TINU. Together, elevated creatinine and β2MG have a positive predictive value of 100% for detecting TINU.
In addition, abdominal plain computed tomograms showed mild enlargement of both kidneys, and renal biopsy results indicated diffuse infiltration of inflammatory cells from the tubulointerstitium to the medulla. Such infiltration is a typical feature of TIN, and these and the laboratory findings led to a diagnosis of TINU.
The patient received methylprednisolone, 1,000 mg/day for three days, and oral prednisolone, 30 mg daily, which was tapered. By Day 40, anterior uveitis had improved, but when the dosage was reduced to 10 mg daily, uveitis recurred, and β2MG and NAG levels increased, so staff decided to continue ocular and oral steroids.