proliferation through pathways involving phosphorylated retinoblastoma protein (pRB). Diagnosis TS can be diagnosed based on clinical observations, but is usually confirmed by histopathology of a lesional biopsy or a plucked spicule. Characteristic histological findings include enlarged and abnormally organized hair follicles and hyperproliferation of inner root sheath cells containing large eosinophilic trichohyalin granules. Antibodies against major capsid protein VP1, the major component of the viral capsid, can be used to confirm the presence of viral particles in cell nuclei. Electron microscopy can also be used to detect viral particles. Quantification of viral load can be performed using quantitative PCR, as affected skin demonstrates much higher viral loads compared to unaffected skin or to asymptomatic individuals who test positive for viral DNA. Differential diagnosis includes other visually similar conditions affecting the hair follicles, many of which appear as drug side effects. A proposed classification system lists TS as one of a group of cutaneous conditions with similar manifestations and distinct etiologies, collectively called the digitate keratoses. Although confirmed TS is rare, the condition is thought to be underdiagnosed. Treatment There have been too few cases of TS reported for a standard treatment to be established. In some cases, improvement in immune function has been noted to produce spontaneous improvement in TS symptoms. This pattern is consistent with the behavior of other viral diseases found in immunocompromised patients, most relevantly with the nephropathy associated in kidney transplant recipients with the polyomavirus BK virus. Antiviral drugs such as valganciclovir and cidofovir have shown benefit in treating this disorder in case reports. Outcomes TS is considered to be a benign dysplasia, although it can be disfiguring and is sometimes itchy. It is not known whether TS lesions have the potential to develop into cancer; while this outcome has never been reported, some polyomaviruses are oncogenic. The natural history of untreated TS is not known and no long-term studies of its progress have been performed. Improvement in immune function has been reported to resolve symptoms in some individual cases. Treatment with antiviral drugs has also been reported to improve symptoms, but only as long as treatment continues. History TS was first described in a 1995 case report as "ciclosporin-induced folliculodystrophy", thought at the time to be an adverse effect of ciclosporin treatment. A subsequent report in 1999, which introduced the term "trichodysplasia spinulosa", used electron microscopy to identify the presence of virus particles in affected