This process is called ochronosis (as the tissue looks ochre); ochronotic tissue is stiffened and unusually brittle, impairing its normal function and causing damage. Diagnosis
If the diagnosis of alkaptonuria is suspected, it can be confirmed or excluded by collecting urine for 24 hours and determining the amount of homogentisic acid by means of chromatography. No assay of HGA in blood has been validated. The Genetic Testing Registry  is used for maintaining information about the genetic test for alkaptonuria.The severity of the symptoms and response to treatment can be quantified through a validated questionnaire titled the AKU Severity Score Index. This  assigns scores to the presence of particular symptoms and features, such as the presence of eye and skin pigmentation, joint pain, heart problems, and organ stones. Treatment
No treatment modality has been unequivocally demonstrated to reduce the complications of alkaptonuria. Main treatment attempts have focused on preventing ochronosis through the reduction of accumulating homogentisic acid. Such commonly recommended treatments include large doses of ascorbic acid (vitamin C) or dietary restriction of amino acids phenylalanine and tyrosine. However, vitamin C treatment does not have definitively proven effectiveness and protein restriction (which can be difficult to adhere to) has not shown to be effective in clinical studies.Several studies have suggested that the herbicide nitisinone may be effective in the treatment of alkaptonuria. Nitisinone inhibits the enzyme 4-hydroxyphenylpyruvate dioxygenase, responsible for converting tyrosine to homogentisic acid, thereby blocking the production and accumulation of HGA.
Diagnosis
The diagnosis of polyneuropathies begins with a history and physical examination to ascertain the pattern of the disease process (such as-arms, legs, distal, proximal) if they fluctuate, and what deficits and pain are involved. If pain is a factor, determining where and how long the pain has been present is important, one also needs to know what disorders are present within the family and what diseases the person may have. Although diseases often are suggested by the physical examination and history alone, tests that may be employed include: electrodiagnostic testing, serum protein electrophoresis, nerve conduction studies, urinalysis, serum creatine kinase (CK) and antibody testing (nerve biopsy is sometimes done).Other tests may be used, especially tests for specific disorders associated with polyneuropathies, quality measures have been developed to diagnose patients with distal symmetrical polyneuropathy (DSP). Differential diagnosis
In terms of the differential diagnosis for polyneuropathy one must look at the following:

Treatment
In the treatment of polyneuropathies one must ascertain and manage the cause, among management activities are: weight decrease, use of a walking aid, and occupational therapist assistance. Additionally, BP control in those with diabetes is helpful, while intravenous immunoglobulin is used for multifocal motor neuropathy.According to Lopate, et al., methylprednisolone is a viable treatment for chronic inflammatory demyelinative polyneuropathy (which can also be treated with intravenous immunoglobulin).