Hallermann–Streiff syndrome is a congenital disorder that affects growth, cranial development, hair-growth, and dental development. There are fewer than 200 people with the syndrome worldwide. One notable organization that is supporting people with Hallermann–Streiff syndrome is the Germany-based "Schattenkinder e.V". Presentation
Patients with this syndrome are shorter than the average person and may not develop hair in many places, including in the facial, leg and pubic areas. Patients also have eye problems including reduced eye size, bilateral cataracts and glaucoma. The syndrome can be associated with sleep apnea. The physical characteristics of the syndrome can result in difficult intubation by medical professionals. Intelligence is usually normal. Cause
The genetic cause of Hallermann–Streiff syndrome has not been conclusively determined. It is most likely due to a de novo mutation, and it may be associated with the GJA1 gene. Diagnosis
Diagnosis is based on the physical characteristics and symptoms. There is no established clinical genetic testing for Hallermann–Streiff syndrome, however some laboratories offer research genetic testing for the condition. Treatment
There is no cure for Hallermann–Streiff syndrome. Treatments center around the particular symptoms in each individual. Early measures are based around ensuring proper breathing and intake of nutrients and may include a tracheostomy. Early surgery for cataracts may be recommended, however some studies have suggested that spontaneous resolution of cataracts occurs in up to 50% of untreated patients.
Adolescents show higher possible mitochondrial inheritance and maternal inheritance than found in adults. Single base-pair and DNA rearrangements in the mitochondrial DNA (mtDNA) have been associated with these traits. Diagnosis
The cause of CVS has not been determined and there are no diagnostic tests for CVS. Several other medical conditions, such as cannabinoid hyperemesis syndrome (CHS), can mimic the same symptoms, and it is important to rule these out. If all other possible causes have been excluded, a diagnosis of CVS using Rome criteria by a physician may be appropriate.Once formal investigations to rule out gastrointestinal or other causes have been conducted, these tests do not need to be repeated in the event of future episodes. Diagnostic criteria
Due to the lack of specific biomarkers available for the disorder, and if all other possible causes can be ruled out (such as intestinal malrotation), physicians rely on the Rome IV process criteria in order to diagnose patients. Patients must meet all three of the following criteria to receive diagnosis: 

Stereotypical episodes of acute vomiting each with a duration of less than 1 week
A history of at least three discrete episodes in the prior year and at least two episodes in the past 6 months, each occurring at least 1 week apart
An absence of vomiting between episodes, but other milder symptoms can be present between cyclesCriteria must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis. A history of family history of migraine headaches can also be used in facilitating diagnosis.