Methemoglobinemia is a rare condition in which the haemoglobin iron is in oxidized or ferric state (Fe3+) and cannot reversibly bind oxygen. Normally, the conversion of ferrous form of iron (Fe2+) to its ferric form (Fe3+) is regulated by NADH methaemoglobin reductase, which results in the reduction of methaemoglobin to haemoglobin. Disruption in the enzyme leads to increased methaemoglobin in the blood. There is tissue hypoxia as Fe3+ cannot bind oxygen, and hence the oxygen-haemoglobin dissociation curve is shifted to the left.

Methemoglobinemia can occur due to congenital or acquired causes. Congenital causes include haemoglobin variants such as HbM and HbH, and deficiency of NADH methaemoglobin reductase. Acquired causes are drugs (e.g. sulphonamides, nitrates, dapsone, sodium nitroprusside, and primaquine) and chemicals (such as aniline dyes).

The features of methemoglobinemia are cyanosis, dyspnoea, anxiety, headache, severe acidosis, arrhythmias, seizures, and loss of consciousness. Patients have normal pO2 but oxygen saturation is decreased. Moreover, presence of chocolate-brown coloured arterial blood (colour does not change with addition of O2) and brown urine also point towards the diagnosis of methemoglobinemia.

Secretin stimulates bicarbonate secretion from the pancreas and liver. VIP induces relaxation of the stomach and gallbladder, secretion of water into pancreatic juice/ bile, and inhibits gastric acid secretion/absorption. CCK classically stimulates gallbladder contraction and relaxation of the sphincter of Oddi. Gastrin stimulates the secretion of HCl by parietal cells in the stomach. Motilin, as the name suggests, increases motility.

A high transferrin saturation is seen in hemochromatosis, as well as a high iron level (>30), a high ferritin level, and a LOW TIBC (<20). Think of it like the opposite findings of iron deficiency anaemia which is a low iron, low ferritin, high TIBC.

The most common causes of a sudden painless loss of vision are as follows:
– Ischaemic optic neuropathy (e.g. temporal arteritis or atherosclerosis)
– Occlusion of central retinal vein
– Occlusion of central retinal artery
– Vitreous haemorrhage
– Retinal detachment

Retinal detachment is a cause of sudden painless loss of vision. It is characterised by a dense shadow starting peripherally and progressing centrally.

Vitreous haemorrhage usually presents with dark spots.

Central retinal artery and central retinal vein occlusion do not usually present with progressing dense shadow.

This man’s lack of ischaemic risk factors makes ischaemic optic neuropathy less likely.

Based on the provided cardiac catheterization results, the following abnormalities are present in this patient:

1. Central Cyanosis: The presence of central cyanosis indicates decreased oxygenation of the blood. This is likely due to an intracardiac shunt, causing unoxygenated blood to mix with oxygenated blood.
2. Right-to-Left Shunt: The saturation readings in the right atrium (60%), right ventricle (55%), and pulmonary artery (55%) are all lower than the expected systemic saturation of 98%. This suggests a right-to-left shunt, allowing deoxygenated blood from the right side of the heart to enter the systemic circulation without passing through the lungs.
3. Pulmonary Hypertension: The pulmonary artery pressure of 20/5 mmHg is elevated compared to normal values, indicating pulmonary hypertension. This could be secondary to increased pulmonary blood flow or resistance, often seen in the presence of a right-to-left shunt.
4. Left-to-Right Shunt: Although not explicitly stated in the results, the elevated left atrial pressure (9 mmHg) suggests increased left-sided filling pressures. This could be due to increased blood flow from a left-to-right shunt, which commonly occurs in congenital heart defects.
5. Normal Left Ventricular Pressure: The left ventricular pressure (110/80 mmHg) falls within normal limits, indicating that the left ventricle is not significantly affected by the shunting.

Based on these findings, a likely diagnosis would be a congenital heart defect causing a right-to-left shunt, such as Tetralogy of Fallot or Eisenmenger syndrome, resulting in central cyanosis and pulmonary hypertension.

Escherichia coli (also known as E. coli) is a gram-negative, facultatively anaerobic, rod-shaped bacterium commonly found in the lower intestine of warm-blooded organisms. Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in their hosts, and are occasionally responsible for product recalls due to food contamination. The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and preventing colonization of the intestine with pathogenic bacteria. Virulent strains can cause gastroenteritis, urinary tract infections, and neonatal meningitis.
The most common causes of neonatal meningitis is bacterial infection of the blood, known as bacteremia (specifically Group B Streptococci (GBS; Streptococcus agalactiae), Escherichia coli, and Listeria monocytogenes). Although there is a low mortality rate in developed countries, there is a 50% prevalence rate of neurodevelopmental disabilities in E. coli and GBS meningitis

Cavitating pneumonia is a complication that can occur with a severe necrotizing pneumonia and in some publications it is used synonymously with the latter term. It is a rare complication in both children and adults. Albeit rare, cavitation is most commonly caused by Streptococcus pneumoniae, and less frequently Aspergillus spp., Legionella spp. and Staphylococcus aureus.

In children, cavitation is associated with severe illness, although cases usually resolve without surgical intervention, and long-term follow-up radiography shows clear lungs without pulmonary sequelae
Although the absolute cavitary rate may not be known, according to one series, necrotizing changes were seen in up to 6.6% of adults with pneumococcal pneumonia. Klebsiella pneumoniae is another organism that is known to cause cavitation.

Causative agents:
Mycobacterium tuberculosis
Klebsiella pneumoniae
Streptococcus pneumoniae
Staphylococcus aureus

Enterococcus faecalis was not found to be a causative agent.

Impetigo appears more commonly on the face than other exposed areas like the limbs. Its blisters are clustered and may have a fluid discharge.

From the given history the patient has NYHA grade III heart failure. He can be safely started on an ACE inhibitor as his serum potassium was towards the lower limit. As there an impairment of renal function, his urea, creatinine and serum electrolytes should be closely monitored after commencing an ACE inhibitor. Adding atenolol will not have any clinical benefit. Increasing the digoxin dose is not needed as the patient is in sinus rhythm. Increasing furosemide will only have symptomatic relief.

Scabies is due to an infestation of Sarcoptes scabiei and most commonly presents with these symptoms. The organism resides in burrows in a pattern specifically affecting the interdigital spaces and the skin folds of the arms and legs. The infection spreads from one person to another, especially in populated communities, through close contact.
Henoch-Schönlein purpura is a type of vascular inflammation.
Psoriasis rash is characterised by scaly plaques affecting the extensor surfaces of the body. Pemphigus vulgaris and bullous pemphigoid both are bullous disorders of the skin. They may present as crusted, weeping, diffuse lesions and there may be involvement in other sites; erosions in the mouth are typically involved in pemphigus vulgaris. Bullous pemphigoid involves the flexural areas and may be associated with a new medication.

Bivalirudin is a competitive, direct thrombin inhibitor. It inhibits both free and clot-bound thrombin and thrombin-induced platelet aggregation. Thrombin enables fibrinogen conversion to fibrin during the coagulation cascade. So inhibition of fibrinogen conversion to fibrin inhibits thrombus development.

Clubbing of the fingers can be present in many clinical conditions like CLD, bronchiectasis, lung abscess, Ulcerative colitis and Crohn’s Disease.

Koilonychia or spoon shaped nails are a typical finding in iron deficiency anaemia.

Splinter haemorrhages are pin point haemorrhages found in infective endocarditis and secondary to trauma.

Yellow nails are present in pulmonary and renal disease.

A case–control study (also known as case–referent study) is a type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute. Case–control studies are often used to identify factors that may contribute to a medical condition by comparing subjects who have that condition/disease (the cases) with patients who do not have the condition/disease but are otherwise similar (the controls).
An odds ratio (OR) is a statistic that quantifies the strength of the association between two events, A and B. The odds ratio is defined as the ratio of the odds of A in the presence of B and the odds of A in the absence of B or vice versa.

Retinal and cerebellar haemangiomas are key features of Von Hippel-Lindau syndrome. Retinal haemangiomas are bilateral in 25% of patients and may lead to vitreous haemorrhage. Von Hippel-Lindau (VHL) syndrome is an autosomal dominant condition predisposing to neoplasia. It is due to an abnormality in the VHL gene located on short arm of chromosome 3.

Generalized Anxiety Disorder (GAD) is characterized by persistent and excessive worry about a number of different things. People with GAD may anticipate disaster and may be overly concerned about money, health, family, work, or other issues. Individuals with GAD find it difficult to control their worry. They may worry more than seems warranted about actual events or may expect the worst even when there is no apparent reason for concern.

GAD is diagnosed when a person finds it difficult to control worry on more days than not for at least six months and has three or more symptoms.

Treatment usually consists of a combination of pharmacotherapy and/or psychotherapy. Antidepressant agents are the drugs of choice in the treatment of anxiety disorders, particularly the newer agents, which have a safer adverse effect profile and higher ease of use than the older tricyclic antidepressants (TCAs), such as selective serotonin reuptake inhibitors (SSRIs).

Downbeat nystagmus (DBN) suggests a lesion in the lower part of the medulla. Arnold-Chiari malformation usually presents with symptoms due to brainstem and lower cranial nerve dysfunction such as DBN.

Night sweats are a B symptom in Hodgkin lymphoma (HL) and imply a poor prognosis.

HL is a malignant proliferation of lymphocytes characterised by the presence of distinctive giant cells known as Reed-Sternberg cells. It has a bimodal age distribution being most common in the third and seventh decades of life.

Staging of HL is done according to the Ann Arbor staging system:

Stage
I: Single lymph node region (I) or one extra lymphatic site (IE)

II: Two or more lymph node regions on same side of the diaphragm (II) or local extra lymphatic extension plus one or more lymph node regions on same side of the diaphragm (IIE)

III: Lymph node regions on both sides of the diaphragm (III) which may be accompanied by local extra lymphatic extension (IIIE)

IV: Diffuse involvement of one or more extra lymphatic organs or sites

Suffix
A: No B symptoms

B: Presence of at least one of the following: unexplained weight loss >10% baseline during 6 months before staging; recurrent unexplained fever >38°C; recurrent night sweats—poor prognosis.

Relative Risk = (Probability of event in exposed group) / (Probability of event in not exposed group). The relative risk is mistaken by some, with the odds ratio and absolute risk. Relative risk is the ratio of the probability of an event occurring with an exposure versus the probability of the event occurring without the exposure. Thus to calculate the relative risk, we must know the exposure status of all individuals (either exposed or not exposed). This implies that relative risk is only appropriate for cases where the exposure status and incidence of disease can be accurately determined such as prospective cohort studies.

The most likely diagnosis is hypertrophic obstructive cardiomyopathy which is suggestive by the history, positive family history and ECG findings. Two-dimensional echocardiography is diagnostic for hypertrophic cardiomyopathy. In general, a summary of echocardiography findings includes abnormal systolic anterior leaflet motion of the mitral valve, LV hypertrophy, left atrial enlargement, small ventricular chamber size, septal hypertrophy with septal-to-free wall ratio greater than 1.4:1, mitral valve prolapse and mitral regurgitation, decreased midaortic flow, and partial systolic closure of the aortic valve in midsystole.

The NICE 2017 guidelines state that in patients who are uncontrolled with a SABA (Salbutamol) and ICS (Inhaled corticosteroid e.g. Beclomethasone), a leukotriene receptor antagonist (LTRA) should be added.
If asthma is uncontrolled in adults (aged 17 and over) on a low dose of ICS as maintenance therapy, offer a leukotriene receptor antagonist (LTRA) in addition to the ICS and review the response to treatment in 4 to 8 weeks.

This recommendation is also stated in NICE 2019 guidelines.

The patient has Cushing syndrome suggested by the elevated 24hr urine free cortisol. Hence, the mass is most probably a cortisol secreting adenoma.

Temazepam is an orally available benzodiazepine used in the therapy of insomnia.
The soporific activity of the benzodiazepines is mediated by their ability to enhance gamma-aminobutyric acid (GABA) mediated inhibition of synaptic transmission through binding to the GABA-A receptor.
The recommended initial dose for insomnia is 7.5 mg before bedtime, increasing as needed to a maximum dose of 30 mg.

The most common side effects of temazepam are dose-related and include daytime drowsiness, lethargy, ataxia, dysarthria, and dizziness.
Tolerance develops to these side effects, but tolerance may also develop to the effects on insomnia.

All the clinical features are suggestive of tricuspid regurgitation. The pansystolic murmur of mitral regurgitation is best heard at the apex.

The most suitable management step for tetanus prevention in this scenario would be to ensure that the individual receives a tetanus toxoid-containing vaccine if they have not had a booster dose within the last five years. Tetanus toxoid-containing vaccines are routinely given during childhood immunization schedules, but booster doses are recommended every 10 years thereafter to maintain immunity. Since the individual’s immunization history is up to date, if they have received their primary series of tetanus vaccinations and a booster dose within the last five years, no further action would be needed regarding tetanus prevention.

However, if the individual’s immunization status is uncertain or if it has been more than five years since their last tetanus booster, they should receive a tetanus toxoid-containing vaccine promptly. Additionally, if the wound is contaminated or considered high risk for tetanus infection, tetanus immune globulin (TIG) may also be administered for immediate protection against tetanus toxins.

Congenital CMV infection can occur when a pregnant woman is infected with the cytomegalovirus (CMV) and passes the virus to her unborn child. Infants infected with CMV during pregnancy can exhibit a range of symptoms, including jaundice, seizures, and microcephaly (abnormally small head size). These symptoms are consistent with congenital CMV infection.

Given the mother’s HIV-positive status, the infant may have been at increased risk of acquiring other infections, including CMV, due to potential immunodeficiency.

The patient presents with worsened renal condition from the last consultation when he was started on enalapril (an ACE inhibitor) so this medication should be stopped. Because there is also no fluid overload; furosemide, a diuretic, should also be stopped.

The most probable diagnosis in this patient is De Clerambault’s syndrome, also known as erotomania, which is a form of paranoid delusion with an amorous quality. The patient, often a single woman, believes that a famous person is in love with her.

Other options:
– Bouffée délirante is an acute psychotic disorder in which hallucinations, delusions or perceptual disturbances are obvious but markedly variable, changing from day to day or even from hour to hour.
– Fregoli delusion is the mistaken belief that some people currently present in the deluded person’s environment (typically a stranger) is a familiar person in disguise.
– Capgras delusion is the belief that significant others have been replaced by impostors, robots or aliens.
– Couvade is the common but poorly understood phenomenon whereby the expectant father experiences somatic symptoms during the pregnancy for which there is no recognized physiological basis.

People with polyarteritis nodosa often exhibit anaemia of chronic disease. Leucocytosis and eosinophilia may also be present. ANCA is only rarely positive. As polyarteritis nodosa affects the kidneys as well, the creatinine is elevated in most cases.

CURB Pneumonia Severity Score estimates the mortality of community-acquired pneumonia to help determine inpatient vs. outpatient treatment.
Select Criteria:
Confusion (abbreviated Mental Test Score <=8) (1 point)
Urea (BUN > 19 mg/dL or 7 mmol/L) (1 point)
Respiratory Rate > 30 per minute (1 point)
Blood Pressure: diastolic < 60 or systolic < 90 mmHg (1 point) The CURB-65 scores range from 0 to 5. Clinical management decisions can be made based on the score:
Score Risk Disposition
0 or 1 – 1.5% mortality – Outpatient care
2 – 9.2% mortality – Inpatient vs. observation admission
≥ 3 – 22% mortality – Inpatient admission with consideration for ICU admission with score of 4 or 5