Night sweats

Night sweats refer to episodes of excessive sweating during sleep that are severe enough to soak clothing or bedding. They can be benign (environmental or idiopathic) but may also signal underlying systemic disease. Persistent night sweats require careful history, examination, and targeted investigations.

🧠 Pathophysiology

• 🌡️ Sweating is mediated by the hypothalamus via sympathetic cholinergic fibres to eccrine sweat glands.
• 🧬 Disruption of thermoregulation occurs with infections, malignancy, endocrine disorders, and some drugs.
• ⚖️ Night sweats often reflect cytokine release (e.g., in infection or cancer), or altered hormonal balance.

🔎 Causes of Night Sweats

• 🦠 Infections: Tuberculosis, HIV, endocarditis, abscesses.
• 🎗️ Malignancy: Lymphoma (classically with fever and weight loss – “B symptoms”), leukaemia.
• 🩺 Endocrine: Hyperthyroidism, diabetes (nocturnal hypoglycaemia), pheochromocytoma, menopause.
• 💊 Medications: Antidepressants (SSRIs, TCAs), antipyretics, steroids, hypoglycaemics.
• 🛌 Benign/Other: Anxiety, idiopathic hyperhidrosis, sleep apnoea, excessive bedding/room heat.

🩺 Clinical Assessment

• 📖 History:
  • Onset, duration, severity, bedding/clothing changes.
  • Associated “red flag” symptoms: fever, weight loss, lymphadenopathy, cough, haemoptysis.
  • Drug history, alcohol use, travel, TB exposure.
  • Family history of malignancy or endocrine disease.
• 👁️ Examination:
  • Vital signs (fever, tachycardia, blood pressure variability).
  • Lymph node survey, organomegaly (liver/spleen).
  • Thyroid exam, cardiac murmurs (endocarditis), pulmonary auscultation.

🧪 Investigations

• 📋 Baseline: FBC, U&E, LFTs, CRP/ESR, thyroid function tests.
• 🦠 Infection screen: HIV, TB (CXR, sputum), blood cultures if systemic features.
• 🎗️ Malignancy: Chest X-ray, LDH, peripheral smear; CT if lymphoma/leukaemia suspected.
• 🧪 Endocrine: HbA1c/glucose (hypoglycaemia), plasma metanephrines (pheochromocytoma).

⚠️ Red Flags

• Unintentional weight loss >10% over 6 months.
• Persistent fever or rigors.
• Generalised lymphadenopathy or splenomegaly.
• Haemoptysis or chronic cough.

🛠️ Management

• 🎯 Treat underlying cause: Anti-TB therapy, chemotherapy for lymphoma, antithyroid drugs, HRT for menopause.
• 🧴 Supportive measures: Sleep hygiene, cooling environment, breathable nightwear, avoidance of alcohol/spicy food before bed.
• 💊 Medication review: Stop or switch offending drugs where possible.
• 📋 Monitoring: Safety-net advice for patients with unexplained sweats pending further investigation.

📊 Differential Diagnosis Table

✅ Take-Home Messages

• Night sweats are common but persistent or severe cases warrant systematic assessment.
• Always ask about red flag symptoms (weight loss, fever, lymphadenopathy).
• Infections and haematological malignancies are important to exclude early in the UK context.
• Medication review is essential – many cases are iatrogenic.

Cases

• Case 1 — Tuberculosis: A 35-year-old man with persistent night sweats, low-grade fever, weight loss, and chronic cough with sputum. Chest X-ray shows upper lobe cavitation. Plan: Sputum AFB smear/culture, HIV test, notify TB service, start anti-TB therapy if confirmed.
• Case 2 — Lymphoma: A 42-year-old woman reports drenching night sweats, unexplained fevers, weight loss, and painless cervical lymphadenopathy. Plan: Urgent haematology referral, excisional lymph node biopsy, staging CT/PET scan, FBC and LDH for prognosis.
• Case 3 — Endocarditis: A 58-year-old man with prosthetic aortic valve presents with recurrent night sweats, fevers, malaise, and new cardiac murmur. Plan: Three sets of blood cultures, echocardiography, IV antibiotics guided by culture, cardiology review.
• Case 4 — HIV Infection: A 28-year-old MSM patient reports weeks of night sweats, oral thrush, fatigue, and weight loss. Plan: Offer HIV testing, screen for opportunistic infections, baseline CD4/viral load, and rapid referral to infectious diseases.
• Case 5 — Occult Malignancy: A 70-year-old ex-smoker presents with persistent night sweats, anorexia, fatigue, and mild anaemia on bloods. No obvious localising features. Plan: Full physical exam, chest/abdominal imaging, tumour markers as indicated, urgent cancer pathway referral.