Junctional epidermolysis bullosa - Skin
All patients having the most severe subtype of generalized JEB, JEB-Herlitz (JEB-H, previously referred to as EB letalis or EB atrophicans generalisata gravis), have mutations within any of the three genes corresponding to the three subunits of the cross-configured extracellular matrix protein laminin-332 (previously named laminin-5). Similarly, the majority of JEB patients with generalized but clinically less severe disease (JEB-non Herlitz [JEB-nH], previously named generalized atrophic benign EB [GABEB] or EB atrophicans generalisata mitis) have structurally less severe mutations within the same three laminin-332 genes. A minority of JEB-nH patients have their mutations instead within the gene encoding for type XVII collagen, which is the same protein that is the primary autoantigen in patients with bullous pemphigoid. Rare subtypes of JEB may have mutations within the genes encoding for other structural proteins residing near or within the hemidesmosome, the most notable example being patients with JEB associated with pyloric atresia (JEB-PA); these patients have their mutations within either of the two genes encoding for the two subunits of a6b4 integrin. A rare genodermatosis named the laryngo-onycho-cutaneous syndrome (LOC syndrome, previously named Shabbir's syndrome), which was recently included among the subtypes of JEB, is notable for having mutations within the gene encoding for the a3 chain of laminin-332. Autosomal recessive mutations of integrin alpha-3 (ITGA3) are associated with junctional skin lesions, interstitial skin disease, and the nephrotic syndrome.
The three most common subtypes of JEB are JEB-H (Herlitz), JEB-nH (non-Herlitz), and JEB inversa, the latter of which is characterized by cutaneous disease activity primarily localized symmetrically to body folds (axillary and inguinal vaults, perineum), nape of the neck, and the lumbosacral area. Both JEB-H and JEB-nH are usually associated with generalized blisters, erosions, atrophic scars, and oftentimes extensive postinflammatory hypo- or depigmentation. A characteristic, if not pathognomonic, finding in JEB-H is the development of thick exuberant granulation tissue in periorificial array, as well as within the nares, upper back and nape of the neck, and periungual folds. The same process may eventually totally occlude the nasal passage and even progress into the uppermost airway. Patients with JEB-H invariably have profound growth retardation and severe multifactorial anemia. The oral cavity and upper esophagus are oftentimes severely affected in JEB-H, as well as in JEB inversa. Findings may include marked microstomia, ankyloglossia, and primary enamel hypoplasia, the latter resulting in pitting of the teeth, severe secondary caries, and eventual premature loss of most or all of the primary and permanent teeth. Esophageal stenoses or strictures may occur in JEB, similar to those seen in severe generalized recessive dystrophic EB. Scarring alopecia of the scalp and delayed puberty are common features of JEB-H. Only about 3% of these patients develop even partial webbing deformities of the hands or feet compared with patients with severe generalized recessive dystrophic EB, who invariably get this deforming musculoskeletal complication.
JEB-nH can be contrasted to JEB-H by the infrequency of clinically significant growth impairment or anemia, lack of exuberant granulation tissue, and relatively mild intraoral disease activity.
Since the characteristic distinguishing clinical features of JEB-H and JEB-nH may not become obvious for at least the first 1 to 2 years of life, some authorities prefer to classify those children as having a "JEB indeterminant subtype" pending more definitive clinical or laboratory data that will allow more precise subclassification and prognostication.
Infants with both JEB-H and JEB-nH run significant risk of death during the first few years of life from sepsis, failure to thrive, and/or upper airway obstruction. As an example, approximately half of all JEB children enrolled in the National (United States) EB Registry died within their first year of life. Tracheolaryngeal obstruction is particularly a major threat in both of these JEB subtypes, and the risk may persist until as late as about age 6. The earliest sign of tracheolaryngeal involvement is a persistent hoarse or weak cry. If progressive, stridor and sudden (and oftentimes fatal) airway obstruction may occur. This is a potential complication that must be carefully watched for, so that lifesaving intervention can be implemented.
As opposed to recessive dystrophic EB, eventual development of potentially lethal squamous cell carcinomas or renal failure are rarely seen in JEB, although these low frequencies may at least in part reflect the limited number of children with generalized JEB who live beyond earliest young adulthood.
The external eye may also be involved in both JEB-H and JEB-nH, resulting in acute onset of severe pain and blistering. If untreated, corneal scarring and even blindness may rarely ensue.
JEB-PA (associated with pyloric atresia) is a very rare EB subtype that can be readily diagnosed during the first day of life, on the basis of clinical and radiological findings of pyloric atresia. Some of these patients also have a variety of genitourinary tract anomalies.
The cutaneous involvement in LOC syndrome (laryngo-onycho-cutaneous syndrome) predominantly involves the facial and neck regions and is associated with particularly severe involvement of the larynx and conjunctiva.
For more information on JEB-H, see OMIM.
For more information on JEB-nH, see OMIM.
Q81.8 – Other epidermolysis bullosa
399971009 – Junctional epidermolysis bullosa
- Other types and subtypes of inherited EB (EB simplex; EB simplex, Dowling-Meara; dystrophic EB)
- Ectodermal dysplasia, including
- Incontinentia pigmenti
- Bullous mastocytosis
- Acrodermatitis enteropathica
- Neonatal herpes simplex
- Bullous impetigo
- Cutaneous porphyrias