Spectrum of ultrasonography findings in nail unit disorders: a pictorial review

Nail unit is affected by a variety of disorders. Diagnosis of nail disorders relies largely on clinical examination, supplemented by biopsy/scrapings of the nail. Imaging such as ultrasound and MRI can aid in better lesion characterization, accurate diagnosis, guiding biopsies and in follow up. Ultrasound is a lucrative modality for nail unit assessment as it is non-invasive, low cost, readily available, can demonstrate all components of the nail unit in high resolution and is real time. MRI on the other hand is expensive, has limited availability and cannot assess multiple nails. This pictorial essay elaborates on the technique of nail ultrasound, anatomy of the nail unit and sonographic appearance of various nail disorders like infections, inflammation, tumors, systemic and rheumatic disorders. The nail plate and nail bed thickness was increased in psoriasis and onychomycosis with increased thickness of extensor tendon and enthesopathies in psoriasis. Glomus tumors appeared as ill-defined, hypoechoic lesions in subungual region with intense color flow. Myxoid cysts were well defined, anechoic, avascular lesions in the proximal nail fold. Periungual fibroma appeared as oval, hypoechoic lesions in subungual region. Onychomatricoma showed interplate echogenicities and increased nail bed thickness.