Individual phenotypic variances in a family with Thiel-Behnke corneal dystrophy

To diagnose Thiel-Behnke dystrophy, an autosomal dominant disease of the anterior basement membrane/Bowman membrane complex and corneal stroma, currently relies primarily on the overall clinical presentation of patient complaints, inheritance pattern, and physical appearance of the corneal findings on slit-lamp examination. Key challenges to accurately identifying the disease are variable and often obscured morphology caused from secondary scarring, creating phenotypic deviation from the "classical" presentation, and mimicry of characteristics typical of other closely related dystrophies. In this report, we demonstrate the high degree of phenotypic variability that can be found in this disease.

A well-characterized family with an established diagnosis of Thiel-Behnke dystrophy mapped to chromosome 10 was evaluated along with the corresponding pedigree. Each individual was examined under slit lamp, and any apparent lesions were photographed.

In total, 4 generations were represented with 20 affected members accounted for, ranging from ages 11 to 86 years. We observed 4 phenotypes in this family: (1) the majority displayed "honeycomb" reticular opacities consistent with Thiel-Behnke dystrophy, (2) several subjects showed more granular-like deposits in a geographic distribution, (3) younger subjects with possible early manifestations of the disease possessed small superficial vesicles, and (4) some eyes exhibited an intermediate form with 2 distinct disease presentations at different regions within the same cornea. Taken together, the pedigree demonstrated a wide continuous spectrum of phenotypes from a supposedly singular genetic disorder that may also vary based on the age of patient.

These observations show that the clinical phenotypic appearance alone can result in a variety of different and conflicting diagnoses. With such potential for error, improvement in the diagnostic criteria is necessary.