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.

The digital rectal examination and sigmoidoscopy are normal, a fact that excludes all the other possible diagnoses. Proctalgia fugax is a functional anorectal disorder characterized by severe, intermittent episodes of rectal pain that are self-limiting. The diagnosis of proctalgia fugax requires exclusion of other causes of rectal or anal pain.

Contrast material poses a greater threat for contrast induced nephropathy. In order to decrease the chance of contrast nephropathy, IV 0.9% saline is considered as the best fluid to maintain blood pressure. Normal Saline helps to expand intravascular volume and decrease the renin angiotensin system activity.

Extradural haemorrhage occurs as a result of head trauma and subsequent acute haemorrhage, primarily from the middle meningeal artery between the skull and the dura mater. Typical symptoms are due to compression of the brain and appear after a lucid interval that follows an initial loss of consciousness. Increased intracranial pressure leads to a decline in mental status and anisocoria, in which the ipsilateral pupil is dilated. Diagnosis is confirmed by CT (biconvex, hyperdense, sharply demarcated mass). Emergency treatment is necessary and involves neurosurgical opening of the skull and hematoma evacuation.

Peroneal nerve injury is also known as foot drop. The common peroneal nerve supplies the ankle and toe extensor muscle groups as well as sensation over the dorsum of the foot; thus, there is also loss of sensation in these cases.

According to the British Thoracic Society, the inability to complete sentences, a HR>110 bpm, a RR>25/min, a PEFR=33-50% of predicted value are all indications of acute severe asthma. Life-threatening asthma would present with hypotension, silent chest, bradycardia and hypoxia.

From the options mentioned here, the closest diagnosis is haemophilia. This is a mixed picture, as a purpuric rash on the buttocks does not correlate with this diagnosis. However, the most appropriate diagnosis is haemophilia.

Only immunoglobulins are required, as he is already immunized.

This patient meets the diagnostic criteria for neutropenic sepsis, which is a relatively common complication of cancer therapy – usually chemotherapy occurring 7-14 days after. It is defined as a neutrophil count of <0.5 x 10^9/L in a patient undergoing anticancer treatment and who has either a temperature higher than 38°C or has other features consistent with clinically significant sepsis. Management approach is the same as mentioned in this case. However, if the patient still remains unwell, then an antifungal such as amphotericin B is started after risk-stratifying the patient and carrying out investigations (e.g. HRCT and Aspergillus PCR) to determine the likelihood of systemic fungal infection.

This case indicates an anaphylactic reaction. The causative factor should be stopped or removed as soon as possible and IM Epinephrine 0.5mg administered. IV Epinephrine can also be considered provided that it is adequately diluted.

Patients with cirrhosis are mostly hyponatraemic due to increased water retention.

Extra-nodal presentation is more common in non-Hodgkin lymphoma (NHL) than in Hodgkin lymphoma (HL). Bone marrow infiltration is more common in low-grade than in high-grade NHLs.

Low-grade NHL is predominantly a disease of older people. Most present with advanced disease, bone marrow infiltration being almost invariable. Anaemia, leucocytosis, and/or thrombocytopaenia in a patient are suggestive of bone marrow involvement. For definitive diagnosis, lymph node biopsy is sufficient.

The other aforementioned statements are ruled out because:
1. Renal impairment in NHL usually occurs as a consequence of ureteric obstruction secondary to intra-abdominal or pelvic lymph node enlargement.

2. Burkitt lymphoma is a high-grade NHL, which was first described in children in West Africa who presented with a jaw tumour, extra-nodal abdominal involvement, and ovarian tumours. It develops most often in children or young adults and is uncommon in older people.

3. High-grade lymphomas are potentially curable. They have a better prognosis and are responsive to chemotherapy unlike low-grade lymphomas, which are incurable with conventional therapy.

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.

Tinea manum is a superficial fungal infection of the hands characterised by dry scaly rash and also involves the interdigital spaces of the hands. Tinea pedis is a fungal infection of feet, whereas onychomycosis represents a fungal infection of the nails, characterised by nail dystrophy, hyperkeratosis. Kerion is the name given to secondarily infected tinea capitis leading to a soft boggy swelling over the scalp. Psoriasis presents as silvery scales over the extensors of the body and it may involve the nails, scalp and joints.

The likely diagnosis in this case is Haemolytic Uremic Syndrome (HUS), which is generally seen in young children presenting with a triad of symptoms, namely: acute renal failure, microangiopathic haemolytic anaemia, and thrombocytopenia. The typical cause of HUS is ingestion of a strain of Escherichia coli. The laboratory results will usually include fragmented RBCs, decreased serum haptoglobin, reduced platelet count, nonspecific WBC changes, and normal coagulation tests (PTT included).

Pneumonia is the predominant clinical manifestation of Legionnaires disease (LD). After an incubation period of 2-10 days, patients typically develop the following nonspecific symptoms:
Fever
Weakness
Fatigue
Malaise
Myalgia
Chills

Respiratory symptoms may not be present initially but develop as the disease progresses. Almost all patients develop a cough, which is initially dry and non-productive, but may become productive, with purulent sputum and, (in rare cases) haemoptysis. Patients may experience chest pain.
Common GI symptoms include diarrhoea (watery and non bloody), nausea, vomiting, and abdominal pain.

Fever is typically present (98%). Temperatures exceeding 40°C occur in 20-60% of patients. Lung examination reveals rales and signs of consolidation late in the disease course.

Males are more than twice as likely as females to develop Legionnaires disease.

Age
Middle-aged and older adults have a high risk of developing Legionnaires disease while it is rare in young adults and children. Among children, more than one third of reported cases have occurred in infants younger than 1 year.

Situations suggesting Legionella disease:
-Gram stains of respiratory samples revealing many polymorphonuclear leukocytes with few or no organisms

-Hyponatremia

-Pneumonia with prominent extrapulmonary manifestations (e.g., diarrhoea, confusion, other neurologic symptoms)

Specific therapy includes antibiotics capable of achieving high intracellular concentrations (e.g., macrolides, quinolones, ketolides, tetracyclines, rifampicin).
Clarithromycin, a new macrolide antibiotic, is at least four times more active in vitro than erythromycin against Legionella pneumophila. In this study the safety and efficacy of orally administered clarithromycin (500 to 1,000 mg bid) in the treatment of Legionella pneumonia were evaluated.
Clarithromycin is a safe effective treatment for patients with severe chest infections due to Legionella pneumophila.

Sarcoidosis is an inflammatory disease that affects one or more organs but most commonly affects the lungs and lymph glands. The inflammation may change the normal structure and possibly the function of the affected organ(s).
The presentation in sarcoidosis varies with the extent and severity of organ involvement, as follows:
Asymptomatic (incidentally detected on chest imaging): Approximately 5% of cases.
Systemic complaints (fever, anorexia): 45% of cases
Pulmonary complaints (dyspnoea on exertion, cough, chest pain, and haemoptysis [rare]): 50% of cases

Löfgren syndrome (fever, bilateral hilar lymphadenopathy, and polyarthralgias): Common in Scandinavian patients, but uncommon in African-American and Japanese patients.

Dermatologic manifestations may include the following:
– Erythema nodosum
– A lower-extremity panniculitis with painful, erythematous nodules (often with Löfgren syndrome)
– Lupus pernio (the most specific associated cutaneous lesion)
– Violaceous rash on the cheeks or nose (common)
– Maculopapular plaques (uncommon)

Staging of sarcoidosis is as follows:
Stage 0: Normal chest radiographic findings
Stage I: Bilateral hilar lymphadenopathy
Stage II: Bilateral hilar lymphadenopathy and infiltrates
Stage III: Infiltrates alone
Stage IV: Fibrosis

Nonsteroidal anti-inflammatory drugs (NSAIDs) are indicated for the treatment of arthralgias and other rheumatic complaints. Patients with stage I sarcoidosis often require only occasional treatment with NSAIDs.

Treatment in patients with pulmonary involvement is as follows:
Asymptomatic patients may not require treatment
In patients with minimal symptoms, serial re-evaluation is prudent
Treatment is indicated for patients with significant respiratory symptoms
Corticosteroids can produce small improvements in the functional vital capacity and in the radiographic appearance in patients with more severe stage II and III disease.

This patient has Stage 1 Sarcoidosis so observation is the most appropriate action.

Patients with compressive neuropathy of the ulnar nerve typically describe numbness and tingling of the ulnar-sided digits of the hand, classically in the small finger and ulnar aspect of the ring finger. Among the general population, symptoms usually begin intermittently and are often worse at night, particularly if the elbow is flexed while sleeping. As the disease progresses, paraesthesia may occur more frequently and during the daytime.

The patient’s chronic renal failure causes decreased renal hydroxylation of vitamin D which leads to decreased calcium absorption in the gut. Simultaneously, there is also decreased renal excretion of phosphate, and this combination of factors results in increased PTH levels.

A head CT scan is the best step to rule out a mass lesion or bleed. Since the patient has symptoms that may suggest elevated intracranial pressure (ICP), a lumbar puncture should be consulted first with a neurologist since it is contraindicated in this case due to raised ICP and risk of coning.

Due to the high amount of ADH in their blood, patient is voiding a low volume of urine with high osmolarity and as a result low levels of electrolytes will be present in the serum.

Hepatitis B full vaccine and Ig should be given to babies born to hepatitis B positive mothers. Hepatitis B vaccine alone or Ig alone is not sufficient to prevent the infection in the new-born baby.

According to the latest research, beta blockers are associated with higher incidence of fatal and non-fatal strokes, all cardiovascular events, and cardiovascular mortality. New-onset diabetes also associates with beta blockers.

Yellow nail syndrome is a very rare medical syndrome that includes pleural effusions, lymphedema (due to under development of the lymphatic vessels) and yellow dystrophic nails. Approximately 40% will also have bronchiectasis. It is also associated with chronic sinusitis and persistent coughing and it usually affects adults.

Bombesin is a tumour marker elevated in small cell lung carcinomas, as well as in gastric carcinomas and retinoblastomas.

Tumour markers can be divided into:
1. Monoclonal antibodies
CA 125: Ovarian cancer, primary peritoneal cancer
CA 19-9: Pancreatic cancer
CA 15-3: Breast cancer

2. Tumour specific antigens
Prostate specific antigen (PSA): Prostatic carcinoma
Alpha-feto protein (AFP): Hepatocellular carcinoma, teratoma
Carcinoembryonic antigen (CEA): Colorectal cancer
S-100: Melanoma, schwannomas
Bombesin: Small cell lung carcinoma, gastric cancer

3. Enzymes
Alkaline phosphatase (ALP)
Neuron specific enolase (NSE)

4. Hormones
Calcitonin
Antidiuretic hormone (ADH)
Human chorionic gonadotropin (hCG)

Euthyroid sick syndrome (also known as nonthyroidal illness syndrome) can be described as abnormal findings on thyroid function tests that occurs in the setting of a nonthyroidal illness (NTI), without pre-existing hypothalamic-pituitary and thyroid gland dysfunction. After recovery from an NTI, these thyroid function test result abnormalities should be completely reversible.
Multiple alterations in serum thyroid function test findings have been recognized in patients with a wide variety of NTIs without evidence of pre-existing thyroid or hypothalamic-pituitary disease. The most prominent alterations are low serum triiodothyronine (T3) and elevated reverse T3 (rT3), leading to the general term low T3 syndrome. Thyroid-stimulating hormone (TSH), thyroxine (T4), free T4 (FT4), and free T4 index (FTI) also are affected in variable degrees based on the severity and duration of the NTI. As the severity of the NTI increases, both serum T3 and T4 levels drop, but they gradually normalize as the patient recovers.
Reverse T3 is used to differentiate between this condition and secondary thyroid failure.

COPD is commonly associated with progressive hypoxemia. Oxygen administration reduces mortality rates in patients with advanced COPD because of the favourable effects on pulmonary hemodynamics.

Long-term oxygen therapy improves survival 2-fold or more in hypoxemic patients with COPD, according to 2 landmark trials, the British Medical Research Council (MRC) study and the US National Heart, Lung and Blood Institute’s Nocturnal Oxygen Therapy Trial (NOTT). Hypoxemia is defined as PaO2 (partial pressure of oxygen in arterial blood) of less than 55 mm Hg or oxygen saturation of less than 90%. Oxygen was used for 15-19 hours per day.

Therefore, specialists recommend long-term oxygen therapy for patients with a PaO2 of less than 55 mm Hg, a PaO2 of less than 59 mm Hg with evidence of polycythaemia, or cor pulmonale. Patients should be evaluated after 1-3 months after initiating therapy, because some patients may not require long-term oxygen.

Biliary atresia is a rare condition that usually becomes symptomatic 2 to 8 weeks after birth. It can be congenital or acquired. Typical symptoms include jaundice, weight loss, dark urine and pale stools.