Tuesday, June 17, 2014

Symbrachydactyly of the Hand: Diagnosis and Presentation

Confirmation of a diagnosis of symbrachydactyly can be challenging.  Most patients who present to my office with symbrachydactyly come in with a different diagnosis- typically amniotic constriction band (also known as constriction band syndrome, amniotic band syndrome, etc)- Amniotic Constriction Band Blog 1Blog 2.   In fact, most patients with any upper extremity diagnosis present with a diagnosis of amniotic constriction band

Most, however, do not have the diagnosis of amniotic constriction band as it has several classic features including the involvement of multiple limbs (i.e., both hands, feet, etc).  These patients may have amputations of the fingers (typically longer digits and the resulting nubbins do not have nails), syndactyly (between scarred, amputated digits) with classic holes (fenestrations) between the fingers, and constriction bands (indentations) in the fingers or toes and forearms and legs. 

Symbrachydactyly in the hand presents in one of 4 ways, as previously noted in several blog posts, symbrachydactyly link including: monodactyly (thumb only), short finger type, peromelia (just nubbins), and cleft type (some thumb and pinky with nubbins between).  Classically, we consider the diagnosis of symbrachydactyly when there are nubbins with fingernails.  This finding reflects the mechanism of this developmental problem- a lack of blood flow to the developing mesoderm (which forms bones and deeper tissues) but a more normal development of the ectoderm (forming nails and fingertips).  This patient shows a classic presentation.

Symbrachydactyly of the hand.  Note the nubbins and the puckered skin. 

Symbrachydactyly of the hand.

Symbrachydactyly in the forearm may be difficult to distinguish from a transverse arrest.  Eventually genetic assessment and a better understanding of limb formation will help us separate the two.  Currently, I use the term transverse arrest for kids with a classic amputation in the forearm.  I use the term symbrachydactyly to describe those kids with a forearm deficiency with nubbins (with or without nails) or even with an invagination of the amputation site.  Again, increasing knowledge will eventually help us separate the two. 

The child shown above was given a diagnosis of symbrachydactyly in our office years ago.  He has functioned well, does not use a prosthetic, and finds his digits helpful to activities (such as tying his shoes).  His only issue is a common complaint: keeping the nubbins and skin depressions clean.  Occasionally, he will get dirt or a foreign body inside and it can become red and inflamed.  Even less commonly, antibiotics are needed.  This family was content to keep the nubbins clean and they were not interested in the surgical option of removing (“smoothing”) the problem areas with surgery.  Obviously, the most functional digits would never be removed surgically but ones that do not provide functional benefit and cause problems can be removed.  In fact, with additional growth, there will be surgical options to stabilize and lengthen these most helpful digits in the symbrachydactyly hand.

Charles A. Goldfarb, MD
My Bio at Washington University

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