Dermatology MCQ - Viral Infections - Trichodysplasia spinulosa

A 55-year-old man who is 6 months post-kidney transplant on immunosuppressive therapy presents with numerous, spiny, follicular papules on his face, particularly on the nose and ears. The lesions are asymptomatic but cosmetically concerning. A skin biopsy reveals enlarged, hypereosinophilic hair follicle inner root sheath cells with intranuclear viral inclusions. Which of the following is the most likely causative agent?

A) Human papillomavirus (HPV)
B) Trichodysplasia spinulosa-associated polyomavirus (TSPyV)
C) Molluscum contagiosum virus
D) Staphylococcus aureus
E)Malassezia species

Correct Answer: B) Trichodysplasia spinulosa-associated polyomavirus (TSPyV)

Explanation

This presentation is classic for trichodysplasia spinulosa (TS), a rare viral folliculitis exclusively seen in immunocompromised patients.

Key Clinical Features of Trichodysplasia Spinulosa:

• Population: Immunocompromised hosts—solid organ transplant recipients (most common), chemotherapy patients, or those with HIV/AIDS.

• Appearance: Numerous, firm, spiny, follicular papules (resisting manual extraction) primarily on the central face (nose, forehead, ears) but can extend to limbs and trunk. The spines are due to aberrant hair shaft formation.

• Symptoms: Typically asymptomatic but can cause pruritus or alopecia in severe cases. It is often a cosmetic concern.

Histopathology:

• Enlarged, hypereosinophilic hair follicle inner root sheath cells with prominent trichohyaline granules.

• Viral inclusions: Large, basophilic intranuclear inclusions that displace chromatin (visible on H&E stain).

• Electron microscopy: Reveals icosahedral viral particles within nuclei.

Virologic Cause:

• Causative Agent: Trichodysplasia spinulosa-associated polyomavirus (TSPyV), a member of the Polyomaviridae family.

• Pathogenesis: TSPyV infects and dysregulates hair follicle keratinocytes, leading to abnormal hair shaft formation and follicular hyperkeratosis.

Why Not the Other Options?

• (A) Human papillomavirus (HPV): Causes warts (verrucous papules) or squamous cell carcinoma, not spiny follicular papules. Biopsy shows koilocytosis, not enlarged inner root sheath cells.

• (C) Molluscum contagiosum virus: Causes umbilicated, pearly papules with central caseous material. Biopsy shows molluscum bodies (large eosinophilic inclusions), not follicular-centric changes.

• (D) Staphylococcus aureus: Causes bacterial folliculitis (pustules), not spiny papules. It responds to antibiotics.

• (E) Malassezia species: Causes pityriasis versicolor (hypopigmented scaly patches) or Malassezia folliculitis (pruritic papulopustules on chest/back), not facial spiny papules.

Management:

• Reduce immunosuppression if possible (e.g., lower dose of tacrolimus).

• Topical cidofovir or oral valganciclovir may be attempted but evidence is limited.

• Spontaneous resolution may occur with immune reconstitution.

Prognosis:
Benign but persistent without intervention. It can cause permanent hair loss if chronic.