The important consideration in these cases is not the horn, but the underlying pathology which may be benign (Seborrheic keratosis, viral warts, histiocytoma, inverted follicular keratosis, verrucous epidermal nevus, molluscum contagiosum, etc.), premalignant (Solar keratosis, arsenical keratosis
, Bowen's disease) or malignant (Squamous cell carcinoma, rarely basal cell carcinoma, metastatic renal carcinoma, granular cell tumour, sebaceous carcinoma or Kaposi's sarcoma.
Malignant transformation may occur but chances are least in punctate porokeratosis.5 The disease should be differentiated from arsenical keratosis
, porokeratotic eccrine ostial and dermal duct nevus, porokeratosis palmaris et plantaris disseminate and punctate porokeratotic keratoderma which may have same presentation.
Papular palmoplantar hyperkeratosis following chronic medical exposure to arsenic: human papillomavirus as a co-factor in the pathogenesis of arsenical keratosis
? Acta Derm Venereol 80:292-293.
appears as diffuse thickening involving palms and soles, alone or in combination with nodules usually symmetrically distributed.
These features were consistent with arsenical keratosis
with superimposed dermatophytosis.
Hypomelanotic guttate macules on diffuse hyperpigmentation and arsenical keratosis
may be formed.
Similarly the premalignant and malignant conditions associated with the horns7,8 include adenoacanthoma, actinic keratosis, Bowen's disease, arsenical keratosis
, Paget's disease, Kaposi sarcoma, malignant melanoma, sebaceous carcinoma9 and squamous cell carcinoma.