Anti-Sm antibodies are essential for diagnosis of SLE, especially in anti-dsDNA-negative patients. ANA are also found in 95% of the patients with SLE but they may also occur with other conditions like Juvenile inflammatory arthritis, chronic activity hepatitis, and Sjogren’s syndrome. Anti-Ro, although also found with SLE are more characteristic of Sjogren Syndrome. RF is usually associated with rheumatoid arthritis and cANCA with Wegener’s granulomatosis, Churg Strauss, and microscopic polyangiitis.

This child has pseudo hypoparathyroidism. It is a heterogeneous group of rare endocrine disorders characterized by normal renal function and resistance to the action of parathyroid hormone (PTH), manifesting with hypocalcaemia, hyperphosphatemia, and increased serum concentration of PTH.
Patients with pseudo hypoparathyroidism type 1a present with a characteristic phenotype collectively called Albright hereditary osteodystrophy (AHO). The constellation of findings includes the following:
Short stature
Stocky habitus
Obesity
Developmental delay
Round face
Dental hypoplasia
Brachymetacarpals
Brachymetatarsals
Soft tissue calcification/ossification
The goals of therapy are to maintain serum total and ionized calcium levels within the reference range to avoid hypercalcaemia and to suppress PTH levels to normal. This is important because elevated PTH levels in patients with PHP can cause increased bone remodelling and lead to hyper-parathyroid bone disease.
The goals of pharmacotherapy are to correct calcium deficiency, to prevent complications, and to reduce morbidity. Intravenous calcium is the initial treatment for all patients with severe symptomatic hypocalcaemia. Administration of oral calcium and 1alpha-hydroxylated vitamin D metabolites, such as calcitriol, remains the mainstay of treatment and should be initiated in every patient with a diagnosis of pseudo hypoparathyroidism.

The question describes a patient who has had an ileal resection. Bile acids are reabsorbed in the distal ileum. Since this has been resected in this patient, one would expect her to have malabsorption of bile acids, causing her diarrhoea. This is a more likely correct answer than a Crohn’s flare, bacterial overgrowth, gastroenteritis, or tropical sprue, given the details included in the question prompt.

Primary aldosteronism now is considered one of the more common causes of secondary hypertension (HTN).
Individuals with primary aldosteronism may present with hypokalaemia metabolic alkalosis; however, as many as 38% of patients with primary aldosteronism may be normokalaemia at presentation.
Routine laboratory studies can show hypernatremia, hypokalaemia, and metabolic alkalosis resulting from the action of aldosterone on the renal distal convoluted tubule (DCT) (i.e., enhancing sodium reabsorption and potassium and hydrogen ion excretion).
Plasma aldosterone/plasma renin activity ratio is used for screening because it is fairly constant over many physiologic conditions.

The patient is clinically free, so Cushing diseases can be exclude.

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.

Cervical radiculopathy is usually due to compression or injury to a nerve root by a herniated disc or degenerative changes. Levels C5 to T1 are the most commonly affected. It is usually, but not always, accompanied by cervical radicular pain, a sharp and shooting pain that travels from the neck and down the upper limb and may be severe. This needs to be differentiated from pain referred from the musculoskeletal (somatic) structures in the neck, which may be aching rather than sharp, and is more severe in the neck than in the upper limb. The neurological signs of cervical radiculopathy depend on the site of the lesion. The patient may have motor dysfunction, sensory deficits or alteration in tendon reflexes. While pain is a common presenting symptom, not all radiculopathies are painful (i.e. only motor deficits may be obvious). CT scanning cannot accurately demonstrate the commonest cause for cervical radiculopathy (disc herniation) without myelography, which requires hospital admission, lumbar puncture and the use of contrast. In patients with cervical radiculopathy, MRI is the imaging technique of choice for the detection of root compression by disc herniation and osteophytes. MRI allows the nerve roots to be directly visualised. Nerve conduction studies are also useful in determining the nerve roots that are involved.

Klinefelter syndrome (KS), the most common human sex chromosome disorder 47,XXY. It is characterized by hypogonadism (micro-orchidism, oligospermia/azoospermia) and gynecomastia in late puberty. If Klinefelter syndrome is not diagnosed prenatally, a patient with 47,XXY karyotype may demonstrate various subtle, age-related clinical signs that would prompt diagnostic testing. These include the following:
Infants: Hypospadias, small phallus, cryptorchidism.
Toddlers: Developmental delay (especially expressive language skills), hypotonia.
Older boys and adolescent males: Tall stature; delayed or incomplete pubertal development with eunuchoid body habitus; gynecomastia; small, firm testes; sparse body hair.

From childhood with progression to early puberty, the pituitary-gonadal function observed is within normal limits for 47,XXY males.
At mid puberty and later, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) concentrations rise to hyper-gonadotropic levels, inhibin B levels fall until they are undetectable, and testosterone levels are at low or low-normal levels after an initial increase.

Fragile X syndrome, also termed Martin-Bell syndrome or marker X syndrome, is the most common cause of inherited mental retardation, intellectual disability, and autism.
However, the patient here does not have any mental disabilities as he already works as a clerk, and that too would make Down’s Syndrome less likely.

Classic Kallmann syndrome (KS) and idiopathic hypogonadotropic hypogonadism (IHH) are rare genetic conditions that encompass the spectrum of isolated hypogonadotropic hypogonadism. Most patients have gonadotropin-releasing hormone (GnRH) deficiency, as suggested by their response to pulsatile GnRH therapy. Hypothalamic-pituitary function is otherwise normal in most patients, and hypothalamic-pituitary imaging reveals no space-occupying lesions. By definition, either anosmia or severe hyposmia is present in patients with Kallmann syndrome, in contrast to patients with idiopathic hypogonadotropic hypogonadism, whose sense of smell is normal.

Myotonic dystrophy is the most likely diagnosis here.
It is a multisystem disorder causing cognitive impairment, cataracts, cardiac problems and testicular atrophy, as well as affecting the muscles. Patients have muscle weakness, normally worse distally, and/or myotonia (which is worse in cold weather).
On examination, patients may also have frontal balding, a myopathic facies, bilateral ptosis, an ophthalmoplegia and wasting of facial muscles and other limb muscles. Myotonic dystrophy is associated with diabetes mellitus and pituitary dysfunction.
Diagnosis is normally based on clinical features with a characteristic electromyogram (EMG) of myotonic discharges. Creatine kinase is generally normal and muscle biopsy is non-specific.

Positive predictive value is the probability that subjects with a positive screening test truly have the disease.

Positive predictive value = true positive / ( true positive + false positive)

The most probable diagnosis considering hypochloraemia and the mild metabolic alkalosis as well as the history of GERD (requiring a high dose of PPI to control) would be bulimia.

Other options:
Diuretic abuse tends to give a hypochloraemic acidosis.
Gitelman syndrome also fits the diagnosis but, it is very rare compared to bulimia.
Inhaled steroid use and stress would not be responsible for such marked electrolyte derangement.

Other potential signs of bulimia nervosa would be parotid gland swelling and dental enamel erosion induced by regular vomiting.