History
A 13-year-old girl attends your clinic with her mother. She is complaining of skin changes affecting her neck, which have been progressively worsening over the past 18 months. In particular the changes are leading to name-calling at school with her peers saying her neck is ‘dirty’. Her school attendance for the last term was only 87 per cent.
She is a very quiet girl and there is little eye contact through the consultation. Both she and her mother acknowledge that she is overweight. Her menarche was at the age of 11 years and 3 months, her menses are irregular. She is not on medication. She is an only child. Her mother has type 2 diabetes, hypertension and is also overweight, her father suffers from asthma.
Examination
Her height is 163 cm and weight 97.5 kg – a body mass index (BMI) of 37 – and blood pressure 140/85 mmHg. She has symmetrical hyperpigmented velvety thickened papil-lomatous plaques associated with scattered skin tags (acrochordons) around her neck, especially posteriorly and laterally, as well as in her axillae (Fig. 42.1) and groin (inter-triginous sites). She has mild to moderately severe comedonal acne over face and chest.
There are longitudinal striae over her lower abdomen and thighs. There is no evidence nof hirsutism.
Questions
• What is the problem affecting this patient’s neck and axillae?
• What is the likely underlying patho-genesis?
• What complications might you con- sider?
Medicine
The hyperpigmented, velvety thickening of the skin in the intertriginous zones, including this patient’s neck and axillae, represent acanthosis nigricans, usually a clinical diagnosis which very rarely requires histological confirmation. It often coexists with acrochordons.
It is thought to be caused by factors that stimulate epidermal keratinocyte and dermal fibroblast proliferation. The most common association with acanthosis nigricans in young patients is insulin resistance. In older patients with new-onset acanthosis nigricans, an associated (usually aggressive) internal malignancy (particularly gastrointestinal) must be considered. Familial and syndromic forms of acanthosis nigricans have also been identi-fied. Many syndromes share common features, including obesity, hyperinsulinaemia and craniosynostosis.
The definition of childhood obesity depends on age-dependent centile charts, however a BMI of 30 kg/m2 is generally accepted as obese. The unfortunate complications of childhood obesity are manifold. It predisposes to insulin resistance and type 2 diabetes, hypertension, hyperlipidaemia, liver and renal disease, reproductive dysfunction and orthopaedic problems. It also increases the risk of adult-onset obesity and cardiovas-cular disease. Emotional and psychosocial sequelae are widespread. Anecdotal evidence suggests that depression and eating disorders are common in children and adolescents referred to obesity clinics. Prejudice and discrimination against individuals with obesity are ubiquitous within youth culture; even very young children have been found to regard their peers who have obesity in negative ways. Social isolation, peer problems, and lower self-esteem are frequently observed. The presence of acanthosis nigricans is an important predictor of metabolic syndrome of insulin resistance and polycystic ovary syndrome in later life unless the BMI is addressed.
Acanthosis nigricans is not a skin disease per se, but rather a sign of an underlying problem. If associated with insulin resistance, the most common cause, treatment of the metabolic abnormality may lead to improvement of the appearance of the skin. Dietary changes and weight loss may cause the acanthosis nigricans to regress almost completely.
KEY POINTS
• Acanthosis nigricans is a marker of underlying medical disorders, most commonly linked with insulin resistance, although amongst older patients acanthosis nigricans may occur as a paraneoplastic phenomenon.
• Identification and treatment of the underlying disorder will improve the appearance of the skin changes.
• In addition this patient’s striae and acne may respond to weight loss.
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