Diagnosis of penicillin allergy

A history of penicillin allergy is relatively common in hospital patients, and is in most not due to type I hypersensitivity reactions.

A diagnosis of penicillin allergy crucially requires a detailed history of the drug reaction, and can be confirmed by a positive skin prick test to the major and minor determinants of penicillin. Skin prick testing is carried out if there is a clinical need for penicillin treatment e.g. treatment of infective endocarditis. A patient is unlikely to develop anaphylaxis with a negative penicillin skin prick test. The detection of penicillin specific IgE in the serum is unreliable.

Further Reading

• Diagnosis and management of penicillin allergy.

Management of infectious diarrhoea

Not all episodes of infectious diarrhoea need treating with antibiotics, and often, resistance to certain antibiotics (e.g. ciprofloxacin) leads to sub-optimal treatment.

Any patient who has been in hospital recently is at risk of C. difficile infection - especially if they may have had antibiotics. This needs to be actively tested for and treated appropriately (metronidazole as first-line treatment, then oral vancomycin). Hence, it is imperative in managing patients with diarrhoea to ensure adequate and suitable stool samples are sent early in the illness. Colonic imaging is usually not indicated in infective colitis (other than a simple X-ray to exclude toxic megacolon) and is only necessary if symptoms persist and stool cultures are negative.

Fig 1: Clostridium Difficile Diarrhoea

Source: Fig 1

Side Effects of Antipsychotics

The side effects of antipsychotics include :

• Extrapyramidal symptoms 
• Stiffness
• Tremor
• Hypersalivation
• Acute dystonia
• Akathisia
• Tardive dyskinesia 
• Anticholinergic symptoms 
• Blurred vision
• Constipation
• Urinary retention
• Dry mouth
• Confusion
• Agitation
• Seizures
• Antihistaminergic symptoms 
• Sedation
• Alpha-blocking effects
• Orthostatic hypotension
• Leucopenia 
• Increased prolactin secretion 
• Amenorrhoea
• Galactorrhoea
• Sexual dysfunction
• Weight gain
• Obstructive jaundice 
• Retinitis pigmentosa (with thioridazine >600 mg/d), 
• Allergic dermatitis / photosensitivity
• Neuroleptic malignant syndrome

Fig 1: Tardive dyskinesia

Akathisia

Acute Dystonia

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Diabetic Eye Disease

Foveal oedema

Fig 1: The fovea: this is the view of an eye a doctor sees looking,  just like a map. The central area of the retina is the 'macula', shown by the dotted black ring. Light focuses here, so any damage may affect a sight. The very central area, the yellow dot, is the the fovea.

Distortion and micropsia arise when the photoreceptors within the deeper layers of the retina become irregularly spaced. Such symptoms are typical of diabetic maculopathy, but not typical of proliferative retinopathy which is characteristically asymptomatic until an acute vitreous haemorrhage occurs.

Cataract occurs at an earlier age than usual in diabetes, but these symptoms are not typical.

Retinal vein occlusion may also present with foveal oedema but is less likely as a cause, especially in a relatively young woman without extra vascular risk factors.

Oral hypoglycaemic medication does not cause foveal damage. Although transient blurring of vision may occur when the blood sugar is first brought under control, this is more typical of type 1 diabetes, in which normalization is more rapid and more profound after using insulin for the first time.

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The appearances are of background diabetic retinopathy with hard exudates in a circular or circinate pattern at the fovea. Blot haemorrhages are also seen, but there are no new vessels to indicate diabetic proliferative retinopathy. The fact that the fovea is involved in this case will mean that the patient’s vision is affected and the eye can be described as showing ‘maculopathy’.

Diabetic maculopathy as seen here will be treated by focal or ‘grid’ laser coagulation, the primary goal being to seal leaking areas close to the fovea.

Crohn’s disease

Crohn’s disease can affect any part of the intestinal tract, and three forms predominate: terminal ileal disease, colitis, and peri-anal Crohn’s. Peri-anal disease is the most infrequent (about 25%).

Crohn’s is frequently associated with a positive family history (in up to 15% of patients), and the genetic component is probably greater than for ulcerative colitis.

Smoking increases the risk of relapse, and 5-ASA compounds only have a modest impact on acute or chronic disease.

Wernicke’s encephalopathy

Wernicke’s encephalopathy typically presents with ophthalmoplegia (horizontal and vertical nystagmus, weakness / paralysis of the lateral rectus muscles, weakness / paralysis of conjugate gaze), ataxia (predominantly affecting stance or gait, and often without clear-cut intention tremor) and confusion.

Horizontal nystagmus

Vertical nystagmus

Lateral rectus muscle

Conjugate gaze

Cryptogenic fibrosing alveolitis (CFA)

In cryptogenic fibrosing alveolitis (CFA) there is predominantly basal disease.

The spirometry is restrictive.

Lung biopsy is rarely performed, only if the clinical or radiological features are atypical.

Steroids have an effect in less than 50% of patients. Lung transplantation may be the only possible treatment for patients with progressive resistant disease.

Fig 1: "Ground glass" appearance in mid and lower zones of both lungs.  There  are also multiple "reticule-nodular" shadowings. 

Fig 2: Spirometry

Source: Fig 2, 

Clostiridium difficile diarrhoea

C. difficile diarrhoea may be newly acquired or may be due to endogenous overgrowth following disruption of the normal flora, usually by antibiotic therapy.

Symptoms may develop as early as one day after exposure to antibiotics, although typically they develop 5 to 10 days after initiation of antibiotic therapy. They can also arise as late as 10 weeks after cessation of antibiotic treatment.

Older patients are at higher risk of developing C. difficile diarrhoea and having recurrent disease than younger people.

C. difficile Toxin A causes disruption of the intercellular tight junctions causing fluid secretion.

Fig 1: Clostridium Difficile Infections

Eosinophilic bronchitis (EB)

Eosinophilic bronchitis (EB) presents with chronic cough and sputum eosinophilia without the abnormalities of airway function seen in asthma. It responds to inhaled corticosteroids. Haemoptysis is not a symptom of EB.

Reference

• Brightling CE, Ward R, Goh KL, Wardlaw AJ, Pavord ID. Eosinophilic bronchitis is an important cause of chronic cough. Am J Respir Crit Med1999; 160: 406–410.

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Paget's disease

Paget's disease of bone is a focal disorder of bone remodelling characterized by an increase in the number and size of osteoclasts in affected skeletal sites while the rest of the skeleton is spared.

Paget’s disease most commonly involves the axial skeleton, the pelvis being the most common, but it can affect any area. In the majority of patients, the disease affects at least two bones, but in one third of patients only one bone is affected. In the skull, the 8th nerve can be compressed, resulting in hearing loss. This is one of the more common complaints, being present in 37% of respondents in a recent survey of 2000 patients with Paget's disease . Other causes of hearing loss include pagetic involvement of the middle ear ossicles, which dampens the motion of these ossicles.

Unlike osteoarthritis, pagetic bone pain usually increases with rest, on weight bearing, when the limbs are warmed, and at night. An estimated 70% of patients who have Paget’s disease have no symptoms. The diagnosis is typically found incidentally on radiographs and laboratory investigations.

Fig 1: Osteoblasts and Osteoclasts

Fig 1: Paget's Disease of Bone

Fig 2: "Cotton Wool' appearance of Paget's Disease

Source: Fig 1, Fig 3,

Atrio-ventricular nodal re-entry tachycardia (AVNRT)

Atrio-ventricular nodal re-entry tachycardia (AVNRT) is caused by a re-entry circuit formed within the AV node causing atria and ventricles to be activated simultaneously. This can cause reflux of jugular venous blood and a sensation of pounding in the throat.

Fig 1: AVNRT
A: During sinus rhythm, condustion occurs through the AV node via a fast beta pathway
B: Typical AVNRT - When an APC fires the beta pathway has a slow refractory time and is temporarily not capable of ante grade conduction. Instead, conduction propagates through a slow alpha pathway. conduction then occurs normally to the ventricle; however, a retrograde impulse can travel through a re-entry loop.
C: Atypical AVNRT - When an APC fires, the beta pathway has fully depolarised and is capable of ante grade conduction. Conduction propagates normally to the ventricle; however a retrograde impulse can travel through the beta pathway and established a re-entry loop.

Acute Blood Loss

Acute loss of blood does not lead to any immediate change in the full blood count: haemodilution takes some time to occur, hence the full blood count can never be used to decide whether or not someone has suffered a significant acute haemorrhage. Physical examination will tell you this, the two most reliable signs of intravascular volume depletion being postural hypotension (lying and sitting) and a reduced jugular venous pressure.

Fig 1: Postural Hypotension

Fig 2: Jugular venous pressure (JVP)

Source: Fig 1, Fig 2,