An absolute neutrophil count (ANC) chronically less than 500/mm3, usually less than 200/mm3, is the main sign of Kostmann's. Other elements include the severity of neutropenia, the chronology (from birth; not emerging later), and other normal findings (hemoglobin, platelets, general body health). Isolated neutropenia in infants can occur in viral infections, autoimmune neutropenia of infancy, bone marrow suppression from a drug or toxin, hypersplenism, and passive placental transfer of maternal IgG.

A bone marrow test can assist in diagnosis. The bone marrow usually shows early granulocyte precursors, but myelopoietic development stops ("arrests") at the promyelocyte and/or myelocyte stage, so that few maturing forms are seen. Neutrophil survival is normal.

Needs mention of (rarer) myelokathexis types. e.g. G6PC3 variant and

Regular administration of exogenous granulocyte colony-stimulating factor (filgrastim) clinically improves neutrophil counts and immune function and is the mainstay of therapy, although this may increase risk for myelofibrosis and acute myeloid leukemia in the long term.

Over 90% of SCN responds to treatment with granulocyte colony-stimulating factor (filgrastim), which has significantly improved survival.

Diagnosis is based on visual examination and the presence of itching. A skin biopsy is often performed to exclude other diseases. Lesion biopsies will typically show a high level of eosinophils in PN. A culture of at least one lesion will rule out staphylococcus infection, which has been significantly linked to atopic dermatitis.

Prurigo nodularis is very hard to treat, but current therapies include steroids, vitamins, cryosurgery, thalidomide and UVB light. In the event that staphylococcus or other infection is present, antibiotics have proven effective, but tend to cause more harm than good for this particular disease.

A physician may administer a strong dose of prednisone, which will almost immediately stop the itch/scratch cycle. However, cessation of steroids allows relapse to occur, usually within a few weeks. Horiuchi "et al" recently reported significant improvement in PN with antibiotic therapy.

Another drug a physician may administer is Apo-Azathioprine. Azathioprine, also known by its brand name Imuran, is an immunosuppressive drug used in organ transplantation and autoimmune diseases and belongs to the chemical class of purine analogues.

The assessment of vitamin B status is essential, as the clinical signs and symptoms in less severe cases are not specific. The three biochemical tests most widely used are the activation coefficient for the erythrocyte enzyme aspartate aminotransferase, plasma PLP concentrations, and the urinary excretion of vitamin B degradation products, specifically urinary PA. Of these, plasma PLP is probably the best single measure, because it reflects tissue stores. Plasma PLP less than 10 nmol/l is indicative of vitamin B deficiency. A PLP concentration greater than 20 nmol/l has been chosen as a level of adequacy for establishing Estimated Average Requirements and Recommended Daily Allowances in the USA. Urinary PA is also an indicator of vitamin B deficiency; levels of less than 3.0 mmol/day is suggestive of vitamin B deficiency.

The classic syndrome for vitamin B deficiency is rare, even in developing countries. A handful of cases were seen between 1952 and 1953, particularly in the United States, and occurred in a small percentage of infants who were fed a formula lacking in pyridoxine.

Adverse effects have been documented from vitamin B supplements, but never from food sources. Damage to the dorsal root ganglia is documented in human cases of overdose of pyridoxine. Although it is a water-soluble vitamin and is excreted in the urine, doses of pyridoxine in excess of the dietary upper limit (UL) over long periods cause painful and ultimately irreversible neurological problems. The primary symptoms are pain and numbness of the extremities. In severe cases, motor neuropathy may occur with "slowing of motor conduction velocities, prolonged F wave latencies, and prolonged sensory latencies in both lower extremities", causing difficulty in walking. Sensory neuropathy typically develops at doses of pyridoxine in excess of 1,000 mg per day, but adverse effects can occur with much less, so doses over 200 mg are not considered safe. Symptoms among women taking lower doses have been reported.

Existing authorizations and valuations vary considerably worldwide. As noted, the U.S. Institute of Medicine set an adult UL at 100 mg/day. The European Community Scientific Committee on Food defined intakes of 50 mg of vitamin B per day as harmful and established a UL of 25 mg/day. The nutrient reference values in Australia and New Zealand recommend an upper limit of 50 mg/day in adults. "The same figure was set for pregnancy and lactation as there is no evidence of teratogenicity at this level. The UL was set based on metabolic body size and growth considerations for all other ages and life stages except infancy. It was not possible to set a UL for infants, so intake is recommended in the form of food, milk or formula." The ULs were set using results of studies involving long-term oral administration of pyridoxine at doses of less than 1 g/day. "A no-observed-adverse-effect level (NOAEL) of 200 mg/day was identified from the studies of Bernstein & Lobitz (1988) and Del Tredici "et al" (1985). These studies involved subjects who had generally been on the supplements for five to six months or less. The study of Dalton and Dalton (1987), however, suggested the symptoms might take substantially longer than this to appear. In this latter retrospective survey, subjects who reported symptoms had been on supplements for 2.9 years, on average. Those reporting no symptoms had taken supplements for 1.9 years."

A number of labs may be helpful in determining the cause of shortness of breath. D-dimer while useful to rule out a pulmonary embolism in those who are at low risk is not of much value if it is positive as it may be positive in a number of conditions that lead to shortness of breath. A low level of brain natriuretic peptide is useful in ruling out congestive heart failure; however, a high level while supportive of the diagnosis could also be due to advanced age, renal failure, acute coronary syndrome, or a large pulmonary embolism.

A chest x-ray is useful to confirm or rule out a pneumothorax, pulmonary edema, or pneumonia. Spiral computed tomography with intravenous radiocontrast is the imaging study of choice to evaluate for pulmonary embolism.

PNE can be caused by pregnancy, scarring due to surgery, accidents and surgical mishaps. Anatomic abnormalities can result in PNE due to the pudendal nerve being fused to different parts of the anatomy, or trapped between the sacrotuberous and sacrospinalis ligaments. Heavy and prolonged bicycling, especially if an inappropriately shaped or incorrectly positioned bicycle seat is used, may eventually thicken the sacrotuberous and/or sacrospinous ligaments and trap the nerve between them, resulting in PNE.

Peripheral neuropathy may first be considered when an individual reports symptoms of numbness, tingling, and pain in feet. After ruling out a lesion in the central nervous system as a cause, diagnosis may be made on the basis of symptoms, laboratory and additional testing, clinical history, and a detailed examination.

During physical examination, specifically a neurological examination, those with generalized peripheral neuropathies most commonly have distal sensory or motor and sensory loss, although those with a pathology (problem) of the nerves may be perfectly normal; may show proximal weakness, as in some inflammatory neuropathies, such as Guillain–Barré syndrome; or may show focal sensory disturbance or weakness, such as in mononeuropathies. Classically, ankle jerk reflex is absent in peripheral neuropathy.

A physical examination will involve testing the deep ankle reflex as well as examining the feet for any ulceration. For large fiber neuropathy, an exam will usually show an abnormally decreased sensation to vibration, which is tested with a 128-Hz tuning fork, and decreased sensation of light touch when touched by a nylon monofilament.

Diagnostic tests include electromyography (EMG) and nerve conduction studies (NCSs), which assess large myelinated nerve fibers. Testing for small-fiber peripheral neuropathies often relates to the autonomic nervous system function of small thinly- and unmyelinated fibers. These tests include a sweat test and a tilt table test. Diagnosis of small fiber involvement in peripheral neuropathy may also involve a skin biopsy in which a 3 mm-thick section of skin is removed from the calf by a punch biopsy, and is used to measure the skin intraepidermal nerve fiber density (IENFD), the density of nerves in the outer layer of the skin. Reduced density of the small nerves in the epidermis supports a diagnosis of small-fiber peripheral neuropathy.

Laboratory tests include blood tests for vitamin B-12 levels, a complete blood count, measurement of thyroid stimulating hormone levels, a comprehensive metabolic panel screening for diabetes and pre-diabetes, and a serum immunofixation test, which tests for antibodies in the blood.

Similar to a tinel sign digital palpitation of the ischial spine may produce pain. In contrast, patients may report temporary relief with a diagnostic pudendal nerve block (see Injections), typically infiltrated near the ischial spine.

Electromyography can be used to measure motor latency along the pudendal nerve. A greater than normal conduction delay can indicate entrapment of the nerve.

Imaging studies using MR neurography may be useful. In patients with unilateral pudendal entrapment in the Alcock's canal, it is typical to see asymmetric swelling and hyperintensity affecting the pudendal neurovascular bundle.

The treatment of peripheral neuropathy varies based on the cause of the condition, and treating the underlying condition can aid in the management of neuropathy. When peripheral neuropathy results from diabetes mellitus or prediabetes, blood sugar management is key to treatment. In prediabetes in particular, strict blood sugar control can significantly alter the course of neuropathy. In peripheral neuropathy that stems from immune-mediated diseases, the underlying condition is treated with intravenous immunoglobulin or steroids. When peripheral neuropathy results from vitamin deficiencies or other disorders, those are treated as well.