The diagnosis is based on the combination of the symptoms. Generally, people are diagnosed with yellow nail syndrome if they have two or three of the three classical symptoms (yellow nails, lymphedema and lung problems). The nail changes are considered essential for the diagnosis, but they can be subtle.

Pulmonary function testing can show obstruction of the airways. People with pleural effusions may show evidence of restriction in lung volumes due to the fluid. Analysis of the fluid in pleural effusions generally shows high levels of protein but low levels of cholesterol and lactate dehydrogenase, but about 30% of effusions are chylous (chylothorax) in that they have the characteristics of lymph.

A lymphogram may be performed in people with lymphedema. This can show both under developed (hypoplastic) lymphatic ducts and dilated ducts. Dye may be found in the skin months after the initial test. Scintigraphy of lymph flow (lymphoscintigraphy) shows delays in drainage of lymph (sometimes asymmetrically), although this test can also be normal.

In 1993, Peter James Dyck divided HSAN I further into five subtypes HSAN IA-E based on the presence of additional features. These features were thought to result from the genetic diversity of HSAN I (i.e. the expression of different genes, different alleles of a single gene, or modifying genes) or environmental factors. Molecular genetic studies later confirmed the genetic diversity of the disease.

Diagnosis is achieved by examining the structure of the chromosomes through karyotyping; while once born, one can do the following to ascertain a diagnosis of the condition:

- MRI

- EEG

This disease is more common in women and an association with the gene FLT4 has been described. FLT4 codes for VEGFR-3, which is implicated in development of the lymphatic system.

Milroy's disease is also known as primary or hereditary lymphedema type 1A or early onset lymphedema.

It is a very rare disease with only about 200 cases reported in the medical literature. Milroy's disease is an autosomal dominant condition caused by a mutation in the FLT4 gene which encodes of the vascular endothelial growth factor receptor 3 (VEGFR-3) gene located on the long arm (q) on chromosome 5 (5q35.3).

In contrast to Milroy's disease (early onset lymphedema type 1A,) which typically has its onset of swelling and edema at birth or during early infancy, hereditary lymphedema type II, known as Meige disease, has its onset around the time of puberty. Meige disease is also an autosomal dominant disease. It has been linked to a mutations in the ‘forkhead’ family transcription factor (FOXC2) gene located on the long arm of chromosome 16 (16q24.3). About 2000 cases have been identified. A third type of hereditary lymphedema, that has an onset after the age of 35 is known as lymph-edema tarda.

Ring chromosome 14 syndrome is extremely rare, the true rate of occurrence is unknown (as it is "less than" 1 per 1,000,000), but there are at least 50 documented cases in the literature.

The diagnosis of HSAN I is based on the observation of symptoms described above and is supported by a family history suggesting autosomal dominant inheritance. The diagnosis is also supported by additional tests, such as nerve conduction studies in the lower limbs to confirm a sensory and motor neuropathy. In sporadic cases, acquired neuropathies, such as the diabetic foot syndrome and alcoholic neuropathy, can be excluded by the use of magnetic resonance imaging and by interdisciplinary discussion between neurologists, dermatologists, and orthopedics.

The diagnosis of the disease has been revolutionized by the identification of the causative genes. The diagnosis is now based on the detection of the mutations by direct sequencing of the genes. Nevertheless, the accurate phenotyping of patients remains crucial in the diagnosis. For pregnant patients, termination of pregnancy is not recommended.

HSAN I must be distinguished from hereditary motor and sensory neuropathy (HMSN) and other types of hereditary sensory and autonomic neuropathies (HSAN II-V). The prominent sensory abnormalities and foot ulcerations are the only signs to separate HSAN I from HMSN. HSAN II can be differentiated from HSAN I as it is inherited as an autosomal recessive trait, it has earlier disease onset, the sensory loss is diffused to the whole body, and it has less or no motor symptoms. HSAN III-V can be easily distinguished from HSAN I because of congenital disease onset. Moreover, these types exhibit typical features, such as the predominant autonomic disturbances in HSAN III or congenital loss of pain and anhidrosis in HSAN IV.

People with yellow nail syndrome have been found to have a moderately reduced lifespan compared to people without the condition.

Early detection is key. Untreated patients usually live 5 to 8 months after diagnosis.

Meige lymphedema, also known as Meige disease, Late-onset lymphedema, and Lymphedema hereditary type 2, is an inherited disease in which patients develop lymphedema. The onset is between the ages of 1 and 35. Other causes of primary lympoedema include Milroy's disease which occurs before the age of 1, and lymphoedema tarda which occurs after the age of 35.

Meige disease,(Hereditary lymphedema type II), has its onset around the time of puberty. It is an autosomal dominant disease. It has been linked to a mutations in the ‘forkhead’ family transcription factor (FOXC2) gene located on the long arm of chromosome 16 (16q24.3). It is the most common form of primary lymphedema, and about 2000 cases have been identified. Meige disease usually causes lymphedema of the legs, however, other areas of the body may be affected, including the arms, face and larynx. Yellow toe nails occur in some individuals.

The most common presentation of Milroy Disease is bilateral lower extremity lymphedema, and may also be accompanied by hydrocele.

The Aagenæs syndrome or Aagenaes syndrome is a syndrome characterised by congenital hypoplasia of lymph vessels, which causes lymphedema of the legs and recurrent cholestasis in infancy, and slow progress to hepatic cirrhosis and giant cell hepatitis with fibrosis of the portal tracts.

The genetic cause is unknown, but it is autosomal recessively inherited and the gene is located to chromosome 15q. A common feature of the condition is a generalised lymphatic anomaly, which may be indicative of the defect being lymphangiogenetic in origin. The condition is particularly frequent in southern Norway, where more than half the cases are reported from, but is found in patients in other parts of Europe and the United States. It is named after Øystein Aagenæs, a Norwegian paediatrician.

It is also called cholestasis-lymphedema syndrome (CLS).

According the Fifth WHO Expert Committee on Filariasis , the most common method of classification of lymphedema is as follows: (The same classification method can be used for both primary and secondary lymphedema)

The International Society of Lymphology (ISL) Staging System is based solely on subjective symptoms, making it prone to substantial observer bias. Imaging modalities have been suggested as useful adjuncts to the ISL staging to clarify the diagnosis. The lymphedema expert Dr. Ming-Huei Cheng developed a Cheng’s Lymphedema Grading tool to assess the severity of extremity lymphedema based on objective limb measurements and providing appropriate options for management.

The treatment of choice is a large resection or amputation of the affected limb. Radiation therapy can precede or follow surgical treatment. Tumors that have advanced locally or have metastasized can be treated with mono or polychemotherapy, systemically or locally. However, chemotherapy and radiation therapy have not been shown to improve survivorship significantly.

Accurate diagnosis and staging are fundamental to the management of lymphedema patients. A swollen limb can result from different conditions that require different treatments. Diagnosis of lymphedema is currently based on history, physical exam, limb measurements, and imaging studies such as lymphoscintigraphy and indocyanine green lymphography. However, the ideal method for lymphedema staging to guide the most appropriate treatment is controversial because of several different proposed protocols.

Lymphedema can occur in both the upper and lower extremities, and in some cases, the head and neck. Assessment of the extremities first begins with a visual inspection. Color, presence of hair, visible veins, size and any sores or ulcerations are noted. Lack of hair may indicate an arterial circulation problem. Given swelling, the extremities' circumference is measured for reference as time continues. In early stages of lymphedema, elevating the limb may reduce or eliminate the swelling. Palpation of the wrist or ankle can determine the degree of swelling; assessment includes a check of the pulses. The axillary or inguinal nodes may be enlarged due to the swelling. Enlargement of the nodes lasting more than three weeks may indicate infection or other illnesses such as sequela from breast cancer surgery requiring further medical attention.

Diagnosis or early detection of lymphedema is difficult. The first signs may be subjective observations such as "my arm feels heavy" or "I have difficulty these days getting rings on and off my fingers". These may be symptomatic of early stage of lymphedema where accumulation of lymph is mild and not detectable by changes in volume or circumference. As lymphedema develops further, definitive diagnosis is commonly based upon an objective measurement of differences between the affected or at-risk limb at the opposite unaffected limb, e.g. in volume or circumference. No generally accepted criterion is definitively diagnostic, although a volume difference of 200 ml between limbs or a 4-cm difference (at a single measurement site or set intervals along the limb) is often used. Bioimpedance measurement (which measures the amount of fluid in a limb) offers greater sensitivity than existing methods.

Chronic venous stasis changes can mimic early lymphedema, but the changes in venous stasis are more often bilateral and symmetric. Lipedema can also mimic lymphedema, however lipedema characteristically spares the feet beginning abruptly at the medial malleoli (ankle level). Lipedema is common in overweight women. As a part of the initial work-up before diagnosing lymphedema, it may be necessary to exclude other potential causes of lower extremity swelling such as renal failure, hypoalbuminemia, congestive heart-failure, protein-losing nephropathy, pulmonary hypertension, obesity, pregnancy and drug-induced edema.

Primary lymphedema is a form of lymphedema which is not directly attributable to another medical condition.

It can be divided into three forms, depending upon age of onset: congenital lymphedema, lymphedema praecox, and lymphedema tarda.

Congenital lymphedema presents at birth. Lymphedema praecox presents from ages 1 to 35. This type of lymphedema accounts for 77–94% of all cases of primary lymphedema. Lymphedema tarda presents after age 35. This type of lymphedema usually develops as a result of a developmental abnormality being precipitated by some insult such as trauma, illness, or physical immobility. Compared to secondary lymphedema, primary lymphedema is more likely to involve the face, conjunctiva, and genitalia in association with any limbs involved.

It can be familial.

Amniotic band syndrome is considered an accidental event and it does not appear to be genetic or hereditary, so the likelihood of it occurring in another pregnancy is remote. The cause of amnion tearing is unknown and as such there are no known preventative measures.

Lymphedema praecox is a condition characterized by swelling of the soft tissues in which an excessive amount of lymph has accumulated, and generally develops in females between the ages of nine and twenty-five.This is the most common form of primary lymphedema, accounting for about 80% of the patients.

Lymphedema–distichiasis syndrome is a medical condition associated with the FOXC2 gene.

Hypotrichosis–lymphedema–telangiectasia syndrome is a congenital syndrome characterized by lymphedema (swelling of tissue due to malformation or malfunction of lymphatics), the presence of telegiectasias (small dilated vessels near the surface of the skin), and hypotrichosis or alopecia (hair loss). Lymphedema usually develops in the lower extremities during puberty. Hair is normal at birth, but usually lost during infancy. Telangiectasias may present on the palms and soles more commonly than on the scalp, legs, and genitalia. The syndrome has been reported in association with both autosomal dominant and autosomal recessive inheritance patterns.

It is associated with a rare mutation of the transcription factor gene "SOX18".

Amniotic band syndrome is often difficult to detect before birth as the individual strands are small and hard to see on ultrasound. Often the bands are detected indirectly because of the constrictions and swelling upon limbs, digits, etc. Misdiagnosis is also common, so if there are any signs of amniotic bands, further detailed ultrasound tests should be done to assess the severity. 3D ultrasound and MRI can be used for more detailed and accurate diagnosis of bands and the resulting damage/danger to the fetus.

Hennekam syndrome also known as intestinal lymphagiectasia–lymphedema–mental retardation syndrome, is an autosomal recessive disorder consisting of intestinal lymphangiectasia, facial anomalies, peripheral lymphedema, and mild to moderate levels of growth and intellectual disability.

It is also known as "lymphedema-lymphangiectasia-mental retardation syndrome".

In a subset of patients it is associated with CCBE1 according research published by its namesake, Raoul Hennekam. Other causal mutations were found in the FAT4 gene. Previously, mutations in the FAT4 gene had been only associated with van Maldergem syndrome. The molecular mechanism of the lymphedema phenotype in CCBE1-associated cases was identified as a diminished ability of the mutated CCBE1 to accelerate and focus the activation of the primary lymphangiogenic growth factor VEGF-C.

This disease is caused by problems in the circulatory system, so when it is presented, in the beginning it is important to follow several recommendations. The person needs to keep the legs elevated as much as possible to help the return of the blood. Whenever sitting down, the person needs to keep the legs on a foot stool. At night it is advisable to sleep with a pillow under the lower legs. In the evening, t is not unusual for legs to be swollen. The volume of the lower leg can increase to up to 100ml after a long working day or up to 200ml after a long-haul flight without moving.

In the example of the 41-year-old Japanese man the lesions were much improved by washing and topical use of corticosteroids for two months, also oral antibiotics like cephalexin are used if cellulitis is present. Moist exudative inflammation and moist ulcers respond to tepid wet compresses of Burow’s solution or just saline or water for 30 to 60 minutes several times a day. But in worse cases, edema that does not disappear spontaneously within a few hours or after a walk, is described as pathological, so it needs to have a special treatment. It is very important to say that Papillamitosis, bilateral and marked edema with few symptoms is mostly caused by the systemic circulation (heart, kidneys, liver).

Papillamitosis is associated, as has been mentioned before, with symptoms and/or clinical signs such as dilated superficial veins, varicose veins and changes in the skin. Edema and its complication Papillamitosis are only partially reversible and soon becomes hard, which is mainly confirmed on palpation. All skin structures are affected and this is characterized by the term. Lymphoedema may develop in many cases accompanied by acral thickening of the skin folds, hyperkeratosis and papillomatosis.

Verruciform xanthoma is uncommon, with a female:male ratio of 1:1.1

There is no uniform prognosis across all patients. Some patients have success managing the symptoms with conservative and/or surgical treatments. Some patients progress to lipo-lymphedema, a condition where lipedema and lipo-lymphedema both occur. Some patients develop Dercum's disease.

Genetic tests and related research are currently being performed at Centogene AG in Rostock, Germany; John and Marcia Carver Nonprofit Genetic Testing Laboratory in Iowa City, IA; GENESIS Center for Medical Genetics in Poznan, Poland; Miraca Genetics Laboratories in Houston, TX; Asper Biotech in Tartu, Estonia; CGC Genetics in Porto, Portugal; CEN4GEN Institute for Genomics and Molecular Diagnostics in Edmonton, Canada; and Reference Laboratory Genetics - Barcelona, Spain.