Skin manifestations of systemic disease — formative SAQs

SAQ 1 (10 marks)

A 9-year-old boy is referred with three weeks of tender, warm, red nodules over both shins, a sore throat two weeks before the onset, and no other symptoms. He is afebrile and systemically well. Separately, a clinic note flags a 13-year-old girl with a velvety, dark, velvety thickening in her neck folds and axillae, a body mass index on the ninety-seventh centile, and a family history of type 2 diabetes. ^[1]

Question: For each child, name the cutaneous sign, state the systemic disease or risk it signals, and outline the targeted work-up and management. Explain the framework that unifies the two presentations. (10 marks) ^[1]

Model answer

The boy — erythema nodosum (3 marks). The tender, warm, bilateral red nodules over the shins are erythema nodosum, a reactive septal panniculitis. In a child with a recent sore throat, the commonest cause is group A streptococcal pharyngitis; the differential also includes tuberculosis, sarcoidosis, inflammatory bowel disease and drugs. The work-up is a throat swab and a rising antistreptolysin-O titre, a chest radiograph, and a tuberculin skin test or interferon-gamma release assay. Management is to treat the trigger — confirm and treat the streptococcal infection — and the nodules resolve over weeks with rest, elevation and non-steroidal anti-inflammatory drugs. They do not ulcerate or scar. ^[1]

The girl — acanthosis nigricans (3 marks). The velvety, hyperpigmented thickening of the neck folds and axillae is acanthosis nigricans, the cutaneous marker of insulin resistance, and in an overweight adolescent with a family history of type 2 diabetes it flags the metabolic syndrome and the risk of progression to type 2 diabetes. The work-up is a fasting glucose or an oral glucose tolerance test, a fasting lipid panel, and a glycosylated haemoglobin in the right child. Management is family-based weight management — nutrition, activity and behavioural change — because the skin improves as the insulin resistance improves, and there is no effective topical treatment for the sign itself. ^[3]

The unifying framework (2 marks). Both children illustrate the principle that the skin is a window to systemic disease. The framework is recognise the sign, investigate the underlying disease it points to, and refer to the right specialist — never treat the skin sign as a primary skin disease, because the lesion is a door and the systemic work-up is the room behind it. ^{[1] [3]}

Disposition (2 marks). The boy is managed as an outpatient with the targeted work-up and treatment of the streptococcal cause, and the nodules are followed to resolution. The girl is managed in the clinic with the metabolic screen and a weight-management programme, and referred to a dietitian and, if glucose intolerance is found, to paediatric endocrinology. Neither requires admission, but the recognition of the systemic link is what makes the management correct. ^{[1] [3]}