Acrokeratosis paraneoplastica
Synonyms and keywords: Bazex syndrome, Acrokeratosis neoplastica

# Overview
Acrokeratosis paraneoplastica is a rare obligate paraneoplastic dermatosis characterized by erythematosquamous lesions localized symmetrically at the acral sites. Acrokeratosis paraneoplastica of Bazex is a cutaneous condition characterized by psoriasiform changes in the hands, feet, ears, and nose, with involvement of the nails and the periungual tissues being characteristic and indistinguishable from psoriatic nails. The condition is associated with carcinomas of the upper aerodigestive tract.

# Pathophysiology
Although the exact mechanism is unclear, several hypothesis have been suggested such as:
- Immunologic mechanisms in which antibodies directed against the tumour cross-react with antigens in the epidermis orbasement membrane
- Tumours capability to secrete growth factors like TGF-alpha that affects epidermal growth and epithelial differentiation
- Genetic susceptibility due to the occurrence of the same HLA types (A3 and B8) in many cases of the disease

# Causes
The etiology of Bazex syndrome is still unknown.

# Differentiating Acrokeratosis Paraneoplastica from Other Diseases
- Psoriasis
- Lichen planus
- Porphyria cutanea tarda
- Epidermolysis bullosa
- Bullous pemphigoid
- Pemphigus

# Epidemiology and Demographics
- Bazex syndrome has been reported almost exclusively in men over the age of 40 years and has unanimously been associated with malignancies.
- There are nearly 140 published cases of Bazex Syndrome.

# Natural History, Complications and Prognosis
- Bazex syndrome is most frequently associated with squamous cell carcinoma (SCC) of the head and neck, particularly of the oral cavity, oropharynx, larynx and esophagus. Association with other malignant tumours including cutaneous squamous cell carcinoma, transitional cell carcinoma of the bladder, metastatic thymic carcinoma, ductal carcinoma of the breast, adenocarcinomas of the colon and prostate, liposarcomas, Hodgkins disease, peripheral T-cell lymphoma, metastatic neuroendocrine tumour, bronchial carcinoid tumour and tumours of the liver, stomach, thymus, uterus, vulva, genitourinary tract and bone marrow are rarely reported.
- Remarkably, 50% of the reported malignancies have metastasis to the cervical lymph nodes; on the other hand, approximately 16% of the cervical lymph nodes metastasis associated with Bazex syndrome have unknown primary tumour.

# Diagnosis

## History and Symptoms
In the majority of the reported cases, cutaneous lesions precede the diagnosis of malignancy by several months.

## Physical Examination
- The main features of this paraneoplasia is the presence of symmetrical papulosquamous eruptions (psoriasiform cutaneous eruptions), nail dystrophy and skin scaling usually localized in the body extremities (acral distribution) which may affect ears, nose, cheeks, hands, feet, fingers, toes, elbows and knees.
- Less frequently, skin bullae and vesicles as well as mucosa alterations can occur concomitantly to the more typical cutaneous lesions.

## Laboratory Findings
- Any clinical sign that could suggest Bazex syndrome should automatically guide a cutaneous biopsy.
- Skin biopsies generally provide a mixture of findings that may be found in several more common disorders like hyperkeratosis, acanthosis, spongiosis, mononuclear perivascular infiltrate, dyskeratotic keratinocytes and vacuolar degeneration of keratinocytes.

## Other Diagnostic Tests
- A complete screening of the upper aerodigestive tract should be done.
- If no tumour is found in the head and neck region, further investigation of other possible affected primary sites or metastasis should be performed, such as mediastinum, colon, bladder, prostate, uterus and vulva.
- Rarely direct immunofluorescence has been positive in patients with Bazex syndrome.

# Treatment
- The definitive therapy is the treatment of the underlying tumour.
- Skin lesions associated with Bazex syndrome seems to be resistant to several therapeutical modalities such as keratolytics, steroids and antibiotics and the nail changes are usually persistent.