Young British singer Cassie Graves lives with Trimethylaminuria, a rare metabolic disorder where the body cannot break down trimethylamine, which is found in certain foods.
The disorder causes the chemical to build up in her system before it is released in her sweat, urine and breath - giving off a strong fishy odour.
Here we take a look at 10 illnesses most people have probably never come across, according to the National Organization for Rare Disorders (NORD).
1. Jumping Frenchmen of Maine
This extreme startle reaction was first identified in the late 1800s among an isolated group of French Canadian lumberjacks. The exact cause of jumping Frenchmen of Maine is unknown, but one theory is that the disorder occurs because of an extreme conditioned response to a particular situation influenced by cultural factors.
2. Parry Romberg Syndrome
In this acquired (not inherited) disorder, skin and soft tissues on half of the face begin to shrink (atrophy), leading to a non-symetrical appearance.
3. Cronkhite-Canada Syndrome
Symptoms of this very rare disease include loss of taste, intestinal polyps, hair loss and nail growth problems. CCS occurs mostly in older people but there have been fewer than 400 cases reported in the past 50 years.
4. Hailey-Hailey Syndrome
This genetic disease is characterised by blisters and lesions that come and go, usually healing without scarring. It becomes apparent after puberty and occurs because of a mutation in a gene responsible for production of a protein essential for good skin health.
Also known as benign chronic familial pemphigus or HHD, Hailey-Hailey occurs due to a mutation in a specific gene that creates a protein that is essential for the proper health of skin.
5. POEMS Syndrome
POEMS stands for Polyneuropathy (affecting many nerves), Organomegaly (abnormal enlargement of an organ), Endocrinopathy (affecting certain hormone-producing glands), Monoclonal gammopathy and skin defects. Symptoms include progressive weakness of the nerves in the arms and legs, enlarged liver or spleen, darkening of the skin and excessive hair growth. Other names for the disorder include Crow-Fukase Syndrome, Takatsuki syndrome and PEP Syndrome.
6. Adult Onset Still's Disease
This rare autoinflammatory disorder (sometimes referred to as AOSD or Wissler-Fanconi Syndrome) affects the entire body but the cause is unknown. It causes high, spiking fevers, a pink or salmon-coloured rash, joint pain, muscle pain and sore throat. Episodes vary in frequency and severity.
7. Necrotizing Fasciitis
This is a rare but very severe type of bacterial infection that can destroy muscles, skin and underlying tissue. "Necrotizing" refers to something that causes tissue death. These infections can be sudden, vicious and fast-spreading, and if not treated quickly, can lead to toxic shock syndrome. Other names for the disease include flesh-eating bacteria (or disease) and streptococcal gangrene.
8. Segawa Syndrome
A rare genetic disorder characterised by an uncoordinated or clumsy manner of walking and dystonia (a general term for a group of muscle disorders characterised by involuntary contractions). Symptoms usually become apparent around six years of age and may be more noticeable in the afternoon or evening than in the morning.
9. Hyperferritinemia-Cataract Syndrome
It is a genetic disease that is characterised by early onset of cataracts associated with persistently elevated levels of a protein known as ferritin in the blood plasma. The mutation associated with this disease is inherited as an autosomal dominant trait, and cataracts are the only known complication associated with this disease.
10. Leukocyte Adhesions Deficiency (LAD) Syndromes
LAD syndromes are characterised by defects affecting how white blood cells respond and travel to the site of a wound or infection. Symptoms vary from person to person, but all who are affected develop an increased susceptibility to recurrent bacterial and fungal infections.