Introduction
Demographics
Causes
Clinical features
Complications
Diagnosis
Differential diagnoses
Treatment
Outcome
Keratosis lichenoides chronica presents with violaceous keratotic papules and nodules arranged in a linear or reticulate pattern on the trunk and limbs, in association with a seborrhoeic dermatitis-like eruption on the face [1,2].
Keratosis lichenoides chronica is also called Nekam disease, lichen verrucosus et reticularis, lichenoid trikeratosis, keratose lichenoide striae, porokeratosis striata lichenoides, and lichen ruber moniliformis.
Keratosis lichenoides chronica is rare, with only around 70 cases reported in the medical literature as of 2019 [1]. It can occur in people of any race, age, or sex. The majority of cases have been described in adults aged 20–40 years; 24% of cases were children [2]. The male to female ratio is 1.73 [2]. Most reported cases have been Caucasians.
The cause of keratosis lichenoides chronica is not well understood. It was initially thought to be a rare variant of lichen planus, but many now consider it to be a distinct condition [1].
Some familial cases of keratosis lichenoides chronica are due to a germline mutation in NLRP1, an inflammasome sensor gene that activates inflammatory cytokines. The aberrant activation of NLRP1 leads to the localised release of interleukin-1, secondary secretion of tumour necrosis factor-alpha and keratinocyte growth factor, resulting in epidermal hyperplasia and keratosis [3,4].
Keratosis lichenoides chronica is characterised by brownish-purple, thick scaly papules or small nodules on the trunk and extremities. The papules are generally arranged in a linear or reticular pattern and are symmetrically distributed. They are usually asymptomatic but can be itchy in 20% of cases. Keratosis lichenoides chronica has a chronic and often progressive course [1].
In 70% of cases, patients also present with facial lesions resembling seborrhoeic dermatitis or rosacea. The lesions are papules or plaques with variable hyperkeratotic scaling that tend to be localised to the convex areas of the face (eg, the forehead, cheeks, nose, and around the eyes and mouth). The nasolabial folds (smile lines) are almost always spared [2].
Other features associated with keratosis lichenoides chronica include [2]:
Keratosis lichenoides chronica has also been reported in conjunction with renal disease, diabetes, hypothyroidism, lymphoma, hepatitis, and tuberculosis [5].
Complications of keratosis lichenoides chronica include visual impairment from ocular manifestations and secondary bacterial infection [2].
The criteria for diagnosing keratosis lichenoides chronica have not been well established [1].
The main differential diagnosis is lichen planus; the features distinguishing keratosis lichenoides chronica from lichen planus are the absence of pruritus, a lack of response to a topical or systemic corticosteroid, and the presence of focal parakeratosis in histological samples.
A skin biopsy is recommended for the histological diagnosis of keratosis lichenoides chronica. Histology typically shows:
Direct immunofluorescence is typically negative [6].
Several other conditions can present with pigmented papules and lichenoid histology. These include:
Keratosis lichenoides chronica is very resistant to available therapies. A recent review found that most patients experience improvement with sun exposure and that oral retinoids (eg, acitretin) and phototherapy, specifically photochemotherapy (PUVA), either alone or in combination are the most effective treatments [2].
Topical agents such as steroid creams are usually ineffective. Systemic agents that have been reported to be useful in some patients include:
Keratosis lichenoides chronica is very difficult to treat, and in most cases, remission is never achieved. Complete resolution has never been reported [2].
