Follicular hyperkeratotic spicules
Most cases of FHS are associated with an underlying multiple myeloma, but idiopathic cases have been rarely reported. FHS primarily affects patients aged 40-70 when associated with multiple myeloma and is seen in idiopathic cases primarily in patients older than 40.
The pathogenesis has not yet been fully elucidated. In many of the reported cases, the myeloma paraprotein is a cryoprotein, and cryoglobulinemia is a co-resenting clinical manifestation. It has been shown in some cases that paraprotein accumulates in the intercellular spaces of the infundibulum, giving rise to parakeratosis and follicular plugs that are composed of paraprotein and parakeratotic cells.
FHS has been reported to resolve with myeloma treatment and reappear with disease recurrence.
L73.9 – Follicular disorder, unspecified
L85.9 – Epidermal thickening, unspecified
81845009 – Follicular hyperkeratosis
Differential Diagnosis & Pitfalls
- Keratosis pilaris and keratosis pilaris atrophicans faciei
- Lichen spinulosus – Predominately found on the extremities and trunk; associated with atopic dermatitis, HIV infection, and ichthyosis.
- Spiky follicular mycosis fungoides – Atypical lymphocytic infiltration of follicles and erythematous, cone-shaped papules surrounding follicles.
- Phrynoderma – Follicular hyperkeratotic papules primarily on the extensor surfaces of the extremities; associated with vitamin A deficiency.
- Trichodysplasia spinulosa – Rare, virally mediated infection associated with immunocompromised patients.
- Demodex-associated hyperkeratotic spicules – Slender spikes seen on the face.
- Drug-induced filiform hyperkeratosis – Reported in association with cyclosporine and sorafenib. Resolves with drug discontinuation.
- HIV-associated follicular spicules – Occurs in concert with pityriasis rubra pilaris and acne conglobata.
- Also, consider trichostasis spinulosa.
- Multiple minute digitate hyperkeratosis – Nonfollicular, hyperkeratotic papules, predominantly found on the extremities and trunk.
- Spiny keratoderma
- Uremic frost